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A 


TEXT-BOOK 


ON 


CHEMISTEY. 


TOR  THE  USE  OF 


SCHOOLS  AND  COLLEGES. 


BV 

JOHN  WILLIAM  DRAPER,  M.D., 

Professor  of  Chemistry  in  the  University  of  New  York,  Member  of  the  American 
Philosophical  Society,  &c. 


With  nearly  Three  Hundred  Illustrations. 


..v4 


NEAV  EDITION. 


NEW  YORK: 

HARPER  & BROTHERS,  PUBLISHERS, 

329  & 331  PEARL  STREET, 
FRANKLIN  SQUARE. 

1854. 


Entered,  according  to  Act  of  Congress,  in  the  year  one  thousand 
eight  hundred  and  fifty-three^  by 

Harper  & Brothers, 

in  the  Clerk’s  Oifice  of  the  District  Court  of  the  Southern  District 
of  New  York. 


3c> 


\2S-if 


BY  THE  SAME  AUTHOR. 

31  ^cxt-Book  on  I^'atural  |})l)iloso|j|)g, 

FOR  THE  USE  OF  SCHOOLS  AND  COLLEGES. 

WITH  NEARLY  400  ILLUSTRATIONS.  l^MO,  SHEEP,  75  CENTS. 


701229 


■-k  , 


'■*1 


. ^ 


PREFACE. 


This  text-book  on  Chemistry,  intended  for  the  use 
of  colleges  and  schools,  contains  the  outline  of  the 
course  of  Lectures  which  I give  every  year  in  this 
University. 

I do  not,  therefore,  present  to  teachers  an  untried 
work.  Its  divisions  and  arrangement  are  the  result 
of  an  experience  of  several  years;  an  experience 
which  has  proved  to  me  that  there  is  required  a text- 
book of  small  size,  so  that  students  can  pass  through 
it  readily  in  the  time  usually  devoted  to  Chemistry. 

Every  instructor  in  this  science  must  have  observ- 
ed that  the  ordinary  Treatises’^  or  Elements”  are 
by  no  means  suited  to  his  wants.  When  they  are 
employed  in  the  class-room,  there  are  large  portions 
which  have  to  be  omitted,  and  other  portions  too 
briefly  explained.  In  fact,  to  study  Chemistry  suc- 
cessfully, the  first  thing  which  is  wanted  is  a com- 
pendious book,  which  sets  forth  in  plain  language  the 
great  features  of  the  science,  without  perplexing  the 
beginner  with  too  much  detail. 

It  will  be  understood,  therefore,  that  this  work, 
with  little  pretensions  to  originality,  except  where  di- 
rectly specified,  occupies  a different  field  from  that  of 
the  larger  treatises.  It  is  intended  as  a manual,  ar- 
ranged in  such  divisions  as  practice  has  shown  to  be 


VI 


PREFACE. 


suitable  for  daily  instruction.  It  is  the  exposition  of 
what  I have  found  to  be  a satisfactory  method  of 
teaching ; and  of  its  success  our  annual  examinations 
are  the  best  testimonial. 

The  unsuitableness  of  large  text-books  has  led  to 
many  attempts  to  reduce  their  size  by  abstracts  and 
compendiums  ; but  the  difficulty  can  never  be  avoid- 
ed by  that  means ; the  very  structure  of  such  works 
is  faulty.  We  never  want  to  use  all  that  an  author 
knows  or  can  possibly  say  on  the  subject.  It  has 
been  well  remarked,  that  ‘‘the  greatest  service  which 
can  be  rendered  to  our  science  is  for  some  person  who 
has  had  the  management  of  large  classes  for  several 
years  to  sit  down  and  write  a book,  setting  forth  what 
he  said  and  what  he  did  every  day  in  his  Lectures. 
That  is  the  thing  we  want.” 

While,  therefore,  this  book  is  offered  to  instructors 
as  a practical  work,  the  object  of  which  is  to  display 
the  leading  features  of  the  science,  I have  endeavored 
to  make  it  a representation  of  the  present  state  of 
Chemistry.  In  this  respect  many  of  our  most  popu- 
lar works  are  defective.  Among  them  I should  not 
know  where  to  turn  for  a simple  exposition  of  the 
Wave  theory  of  Light  or  of  Ohm’s  theory  of  Voltaic 
Currents ; yet  the  one  is  the  most  striking  result  of 
physical  research,  and  the  other  is  connected  with  the 
fundamental  facts  of  Electro-chemistry. 

To  the  treatises  of  Hare,  Kane,  Grraham,  Grregory, 
Fownes,  Dumas,  and  Millon  I must  formally  state 
my  obligations.  In  Descriptive  Chemistry  I have 
followed  them  closely ; and  in  those  cases  Avhich  are 
much  more  common  than  is  generally  supposed,  where 
there  are  differences  in  the  imputed  properties  of  bod- 


PREFACE. 


Vll 


ies,  I have  consulted,  wherever  1 could,  either  original 
memoirs  or  the  annual  reports  of  Berzelius. 

The  number  of  wood -cuts,  representing  experi- 
mental arrangements,  which  have  been  introduced, 
will  give  to  a beginner  a clearer  idea  of  the  practical 
part  of  each  Lecture,  and,  in  our  country  colleges, 
may  sometimes  supply  the  place  of  defective  or  in- 
complete apparatus.  To  each  Lecture  is  appended  a 
set  of  questions.  They  enable  a young  student  more 
quickly  to  apprehend  the  doctrines  which  are  before 
him. 


University  of  New  York, 
July  6,  1846. 


John  William  Draper. 


PREFACE  TO  THE  NEW  EDITION. 


The  favor  with  which  this  hook  has  been  received 
by  the  public,  so  many  editions  of  it  having  been 
called  for,  has  led  me  to  give  it  a thorough  revision, 
with  a view  of  bringing  it  to  the  present  condition  of 
the  science. 

The  reader  will  find  that  extensive  changes  have 
been  made  in  those  parts  which  treat  of  the  impon- 
derable principles,  several  of  the  Lectures  having 
been  entirely  rewritten. 

I hope  that  the  alterations  and  additions  now  pre- 
sented will  secure  for  the  work  a continuance  of 
that  patronage  which  it  has  hitherto  so  extensively 
received. 

John  W.  Draper. 

University  of  New  York,  ) 

July  80,  1853  ) 


CONTENTS 


I.ecture  I Page 

I.  Constitution  of  Matter  1 

II.  Constitution  of  Matter  {continued) " 6 

III.  Heat....... 11 

IV.  Expansion  of  Gases  and  Liquids 15 

V.  Expansion  of  Liquids  and  Solids T 21 

VI.  Expansion  of  Solids 25 

VII.  Capacity  of  Bodies  for  Heat  29 

VIII.  Capacity  for  Heat  and  Latent  Heat 34 

IX.  Latent  Heat  {continued) 39 

X.  Vaporization 43 

XL  Ebullition 48 

XII.  Vaporization 52 

XIII.  Evaporation  and  Interstitial  Radiation 58 

XIV.  Conduction 64 

XV.  Radiation 67 

XVI.  Theory  of  the  Exchanges  of  Heat 72 

XVII.  Nature  of  Light 75 

XVIII.  Constitution  of  the  Solar  Spectrum 80 

XIX.  Wave  Theory  of  Light *. . . 84 

XX.  Wave  Theory  of  Light  {continued)  . * . . . 87 

XXI.  Wave  Theory  of  Light  {continued)  91 

XXII.  Production  of  Light 95 

XXIII.  Chemical  Action  of  Light 99 

XXIV.  Chemical  Action  of  Light  {continued) 102 

XXV.  Electricity  105 

XXVL  Theory  of  Electrical  Induction  109 

XXVII.  Laws  of  the  Distribution  of  Electricity  and  General  The- 
ories   * 113 

XXVIII.  Faraday’s  Theory  of  Electrical  Polarization 117 

XXIX.  Voltaic  Electricity 123 

XXX.  Effects  of  Voltaic  Electricity 127 

XXXI.  The  Electro-chemical  Theory * 133 

XXXII.  Ohm’s  Theory  of  the  Voltaic  Pile — Magnetism 138 

XXXIII.  Electro-dynamics — Thermo-electricity 145 

XXXIV.  The  Chemical  Nomenclature  ...» 153 

XXXV.  The  Symbols 156 

XXXVI.  The  Laws,  of  Combination * 160 

XXXVll.  Constitution  of  Bodies — Crystallization 164 


X 


CONTENTS. 


I.ecture 

XXXVIII.  Chemical  Affinity 

XXXIX.  Pneumatic  Chemistry — Oxygen  Gas 

XL.  Oxygen  {continued) 

XLI.  Hydrogen 

XLII.  AVater 

XLIII.  Nitrogen — Atmospheric  Air 

XLIV.  Atmospheric  Air  {continued)  . . . '. 

XLV.  Atmospheric  Air  {continued) 

XL VI.  Compounds  of  Nitrogen  and  Oxygen 

XLVII.  Compounds  of  Nitrogen  and  Oxygen 

XLVIII.  Sulphur : 

XLIX.  Compounds  of  Sulphur  and  Oxygen 

L.  Sulphur  and  Phosphorus  ......  

LI.  Compounds  of  Phosphorus  and  Oxygen — Chlorine 

LII.  Chlorine  {continued) 

LIII.  Chlorine  {continued) — Iodine 

LIV.  Bromine — Fluorine — Carbon  

LV.  Carbonic  Acid 

LVI.  Cyanogen — Boron— Silicon— Ammonium 

LVII.  General  Properties  of  the  Metals 

LVIll.  Potassium 

LIX.  Sodium — Lithium— Barium 

LX.  Strontium— Calcium — Magnesium — Aluminum 

LXI.  Manganese — Iron  

LXII.  Iron — Nickel — Cobalt — Zinc 

LXIII.  Cadmium — Tin — Chromium — Titanium 

LXIV.  Argenic 

LX V.  Arsenic — Antimony — Tellurium — Uranium — Copper 

LX VI.  Lead — ;Bismuth— Silver  

LXVII.  Mercury— Gold— Platinum,  &c 

V LXVIII.  General  Properties  of  Organic  Bodies 

LXIX.  The  Non-nitrogenized  .Bodies  , . v , , 

LXX.  Action  of  Agents  on  the  Starch  Group 

LXXI.  The  Metamorphosis  of  the  Starch  Group  by  Nitrogenized 

Ferments  ^ 

LXXII.  The  Derivatives  of  Fermentative  Processes 

LXXIII.  The  Derivative  Bodies  of  4lcph,ol 

LXXIV.  Oxydation  of  AJcohol 

LXXV,  Deriyatiyes  .of  Acetyle — the  Kakodyle  Group 

LXXVI.  The  Wood-Spirit  Group.... 

LXXyiL  .The  Potato-Oil  Group — the  Benzyle  Group 

LXXVIIL  The  Salicyle  nnd Cinnamyle  Groups. 

LXXIX.  The  Nitrogenized  Principles— Ammonia — Cyanogen, .... 

LXXX.  Bodies  nUi.ed  to  .Cyanogen 

LXXXP  Mellone-tJrea 


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249 

253 

260 

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268 

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285 

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295 

299 

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314 

318 

322 

326 

329 

334 

337 

341 

345 

348 

352 

356 

361 

364 


CONTENTS.  - Xi 

Lecture  Page 

LXXXIf.  The  Vegetable  Acids 368 

LXXXIII.  The  Vegetable  Alkalies 373 

LXXXIV.  The  Coloring  Principles 377 

LXXXV.  The  Fatty  Bodies 381 

LXXXVI.  The  Resins,  Balsams,  and  Bodies  arising  in  destructive 

Distillation 385 

LXXXVIL  Animal  Chemistry — Digestion  and  Nutrition 389 

LXXXVIII.  Origin  and  Deposit  of  the  Fats  and  Neutral  Nitrogenized 

Bodies 393 

LXXXIX.  The  Transmission  of  Food  through  the  System 397 

XC.  Nature  of  the  Processes  of  Secretion 401 


INTRODUCTION. 

CONSTITUTION  AND  GENERAL  PROPERTIES  OF  MATTER. 


LECTURE  I. 

Constitution  of  Matter. — Distinction  between  Chem 
istry  and  Natural  Philosophy. — General  Division  oj 
Chemistry. — Active  Forces  and  Ponderable  Bodies. — 
Proof  of  the  Atomic  Constitution  of  Matter  in  the  Casez 
of  a Solid  and  a Gas. — Atoms  are  incojiceivably  small 
— They  are  not  in  contact — They  are  unchangeable 
and  indestructible. 

The  physical  sciences  are  divided  into  two  classes,  com- 
prehended respectively  under  the  titles  of  Natural  Phi- 
losophy and  Chemistry. 

Natural  Philosophy  investigates  the  relations  of  masses 
to  one  another.  The  movements  of  tides  in  the  sea  under 
the  conjoint  influence  of  the  sun  and  moon  ; the  descent  of 
falling  bodies  to  the  earth  ; the  pressure  of  the  atmosphere  ; 
the  various  modes  of  rendering  mechanical  forces  available, 
by  the  action  of  levers,  pulleys,  wedges,  screws ; the  phe- 
nomena of  the  planetary  bodies,  which  move  in  elliptic  orb- 
its around  a central  mass  : these  are  all  objects  for  the  con- 
sideration of  Natural  Philosophy. 

Chemistry  considers  the  relations  of  particles  to  each 
other ; it  investigates  the  properties  and  qualities  of  differ- 
ent kinds  of  matter,  their  mutual  influence,  and  the  action 
of  the  imponderable  principles  upon  them.  It  treats  of  the 
causes  of  those  invisible  movements  which  the  molecules 
of  bodies  around  us  unceasingly  undergo.  It  also  includes 
many  of  the  phenomena  of  living  beings,  explains  the  objects 
of  respiration,  digestion,  and  other  such  animal  functions. 

Every  change  taking  place  in  bodies  is  due  to  the  oper- 
ation of  some  active  force.  It  is  one  of  the  first  principles 
in  philosophy,  that  no  movement  or  mutation  can  occur  in 

Into  what  classes  are  the  physical  sciences  divided  ? Of  what  phenom- 
ena does  natural  philosophy  treat  ? What  are  the  objects  of  chemistry  ? 

K 


2 


CONSTITUTION  OF  MATTER, 


any  thing  spontaneously  ; we  must  always  refer  it  to  a dis- 
turbing  cause.  Under  the  influence  of  heat,  bodies  increase 
in  size ; under  that  of  electricity,  some  are  dissevered  into 
their  component  elements  ; under  that  of  liglit,  vegetables 
form  from  inorganic  materials  their  organized  structures. 
The  science  of  chemistry  resolves  itself,  therefore,  into  two 
divisions  : the  first,  embracing  the  consideration  of  the  act- 
ive forces  of  chemistry ; the  second,  the  objects  on  which 
those  forces  operate. 

These  active  forces  are  Heat,  Light,  and  Electricity.  By 
the  older  chemists  they  are  designated  as  imponderable  sub- 
stances, from  the  circumstance  that  they  do  not  affect  the 
most  sensitive  balances. 

We  can  form  no  idea  of  the  properties  of  bodies  disen- 
gaged from  the  influence  of  these  principles.  Thus  we  find 
all  material  substances  existing  under  one  of  three  condi- 
tions, solid,  or  liquid,  or  gaseous ; and  the  majority  can  as- 
sume either  of  these  conditions  under  the  influence  of  heat. 
Water,  for  instance,  at  low  temperatures,  exists  in  the  solid 
state  as  ice  ; at  higher  temperatures,  it  assumes  the  liquid 
condition ; and  at  still  higher,  exhibits  the  gaseous  form. 
We  see,  therefore,  that  it  is  the  degree  of  heat  to  which  it 
is  exposed  which  determines  its  physical  state. 

One  of  the  first  problems  which  the  chemist  has  to  solve 
is  that  of  determining  the  true  constitution  of  matter ; not 
of  matter  in  the  abstract,  but  as  placed  under  the  influence 
of  these  external  powers. 

All  the  phenomena  of  chemistry  prove  that  material  sub- 
stances consist  of  indivisible  and  exceedingly  minute  por- 
tions, called  Atoms,  which  are  placed 
at  certain  distances  from  one  another, 
those  distances  being  variable,  and  de- 
termined by  the  agency  of  active  forces. 

Thus,  if  we  take  a copper  ball,  a, 
Fig.  1,  an  inch  in  diameter,  and  pro- 
vide a ring,  b,  of  such  a size  that  the 
ball  at  common  temperatures  can  read- 
ily pass  through  it,  and  having  sus- 
pended the  ball  by  means  of  a chain  to  a stand,  d,  expose 

What  are  the  two  leading  divisions  of  chemistry  ? What  are  the  active 
forces  of  chemistry?  Why  are  these  called  imponderable  bodies?  What 
are  the  three  forms  of  substances  ? What  is  it  that  determines  these  forms  ? 
What  is  the  constitution  of  matter?  Describe  the  arrangement  of  the  in- 
stviunf^nt,  1,  and  its  use. 


Fig.  1. 


CONSTITUTION  OF  MATTER. 


3 


it  to  the  flame  of  a spirit  lamp,  c,  as  it  becomes  warm  it  will 
be  found  to  dilate^  so  that,  in  the  course  of  a few  minutes, 
it  can  no  longer  pass  readily  through  the  ring,  but  if  placed 
thereon,  remains  supported. 

While,  under  these  circumstances,  no  visible  change  has 
taken  place  in  the  general  properties  of  the  ball,  its  weight 
remaining  the  same  as  before,  its  aspect  is  the  same.  We 
conclude,  therefore,  that  its  volume  has  increased  because 
we  have  raised  its  temperature. 

But  now,  the  lamp  being  removed,  the  ball,  still  resting 
on  its  ring,  begins  to  cool.  In  the  course  of  a few  minutes 
it  spontaneously  drops  through  the  ring.  It  has,  therefore, 
become  less  than  it  was  while  hot,  and,  in  point  of  fact, 
when  its  original  temperature  is  reached,  it  has  recovered 
its  original  size. 

From  this  simple  but  beautiful  experiment,  very  import- 
ant conclusions  may  be  drawn.  The  copper  ball,  in  cooling, 
becomes  less  : a fact  which  at  once  suggests  the  idea  that 
its  constituent  particles  have  approached  each  other.  In 
its  warm  and  dilated  state,  although  it  exhibited  no  ap- 
pearance of  transparency,  or  of  interstitial  spaces,  or  pores 
through  which  light  might  pass,  its  particles  were  not  touch- 
ing one  another,  for  had  they  been  in  actual  contact  they 
could  not  have  more  closely  approached  one  another,  and 
contraction  could  not  have  taken  place. 

As  all  bodies  contract  during  the  act  of  cooling,  we  infer 
that  the  particles  of  which  they  are  composed  are  separated 
from  each  other  by  intervening  spaces,  and  experiments  such 
as,  that  we  have  been  considering  suggest  two  important 
observations:  1st.  That  all  material  substances  are  made 
up  of  small  particles  which  do  not  touch  each  other  ; and, 
2d.  That  the  intervening  spaces  may  be 
varied  at  the  pleasure  of  the  experimenter. 

Let  us  consider  a second  illustration 
which  will  lead  us  to  the  same  conclusion, 
selecting  as  the  object  of  our  experiment 
atmospheric  air,  a substance  differing  in  all 
its  physical  and  chemical  relations  from 
the  copper  ball.  Let  us  take  a tube  of 
glass  half  an  inch  in  diameter,  and  bent 


^ Why,  in  this  experiment,  docs  the  ball  finally  drop  through  the  ring? 
Could  contraction  take  place  if  its  particles  were  already  in  contact  ? What 
two  conclusions  do  these  facts  suggest? 


4 


CONSTITUTION  OF  MATTER. 


in  the  form  exhibited  in  Fig.  2,  a,  c,  d.  The  tube  is  closed 
at  its  upper  end,  a ; it  is  bent  at  c,  and  over  its  open  extrem- 
ity, at  d,  a bag  of  India  rubber  ts  tied,  air  tight.  In  the  tube 
there  has  been  previously  inclosed  a sufficient  quantity  of 
water  to  fill  all  the  portion  h,  c,  d,  but  the  space  from  a to 
h is  occupied  by  atmospheric  air.  It  is  to  the  volume  of  this 
atmospheric  air  that  our  attention  is  directed. 

If  we  compress  the  India  rubber  bag  in  our  hand,  the  vol- 
ume of  the  air  instantly  becomes  less,  the  diminution  being 
greater  in  proportion  as  the  pressure  is  greater.  Now  it  is 
inconceivable  that  this  phenomenon  should  ensue  unless 
the  aerial  particles  approached  each  other  ; but  such  an  ap- 
proach would  be  impossible  if  they  were  already  in  contact. 
Two  particles  could  not  occupy  the  same  space  at  the  same 
time. 

We  conclude,  therefore,  that  for  atmospheric  air,  a gaseous 
body,  as  well  as  for  copper,  a solid,  the  same  law  holds  good, 
and  that  both  these  forms  of  matter  are  constructed  upon 
the  same  type  ; that  they  are  made  up  of  particles  set  at 
distances  from  one  another,  and  that  we  can  change  those 
distances  at  pleasure  by  resorting  to  changes  of  temperature 
or  to  mechanical  forces. 

It  is  worthy  of  observation,  that  by  proper 
means  these  interstitial  spaces  may  be  greatly 
increased  or  diminished,  and  in  very  many  in- 
stances without  any  striking  apparent  change 
occurring  in  the  substance  under  experiment. 
Thus,  if  we  take  a globe  of  glass  two  or  three 
inches  in  diameter,  a,  Fig.  3,  with  a neck  or 
tube,  proceeding  from  it,  and  fill  the  globe  full 
of  water,  with  the  exception  of  a small  bubble  of  air  which 
occupies  its  upper  part,  while  the  open  extremity  of  the  tube, 
b,  dips  beneath  some  Avater  contained  in  a glass  jar,  c,  then, 
covering  the  whole  with  an  air-pump  receiver,  d,  proceed  to 
exhaust,  we  shall  find  that  the  little  bubble,  dilates  as 
the  machine  is  worked,  and  may  be  rendered  a hundred-fold 
greater  than  at  first.  In  this  expanded  condition,  its  par- 
ticles must  have  greatly  receded  from  each  other,  and  yet 
no  remarkable  physical  change  is  to  be  observed.  There 

Describe  the  instrument  represented  in  Fig.  2.  What  is  the  use  of  this 
instrument  ? With  an  increase  of  pressure,  what  happens  to  the  included 
air?  Can  two  particles  occupy  the  same  space  at  the  same  time  ? What, 
then,  is  the  deduction  from  this  experiment  ? What  is  the  experiment  given 
in  Fig.  3 intended  to  illustrate  ? 


Fig.  3. 


SIZE  OF  ATOMS. 


5 


are  no  dark  or  vacuous  spaces ; but  in  this  attenuated  con- 
dition, it  possesses  the  aspect  which  it  had  when  at  the 
common  density. 

With  these  preliminary  facts,  we  may  now  direct  our  at- 
tention, 1st,  to  the  properties  of  atoms  ; and,  2d,  to  the  inter- 
stitial spaces  which  part  them  from  each  other. 

That  the  atoms  of  which  bodies  are  composed  are  exceed- 
ingly small,  we  possess  abundant  proof  By  dissolving  sub- 
stances in  liquid  media,  and  then  greatly  diluting  the  solu- 
tion, we  can  effect  a subdivision  to  an  incredible  extent.  A 
single  drop  of  a solution  of  sulphate  of  indigo  will  commu- 
nicate a blue  color  to  one  thousand  cubic  inches  of  water, 
so  that  every  drop  of  that  diluted  solution  contains  a portion 
of  the  coloring  matter.  In  the  same  manner,  by  resorting 
to  proper  tests,  we  can  show  that  a grain  of  copper,  or  silver, 
or  gold,  may  be  divided  into  many  millions  of  smaller  parts, 
each  of  which  may  be  readily  recognized.  Nor  is  it  alone 
by  these  chemical  processes  that  such  a minute  subdivision 
may  be  effeeted  : by  the  mechanical  process  of  beating  with 
a hammer,  gold  may  be  extended  into  leaves  which  are  less 
than  the  2 oo\)  (r()  inch  thick,  a dimension  far  less 

than  the  human  eye,  unassisted  by  microscopes,  can  discover, 
for  the  smallest  spherical  object  visible  to  it  is  about  20^00 
part  of  an  inch  in  .diameter.  By  other  processes,  it  has  been 
estimated  that  this  metal  may  be  divided  to  such  an  extent, 
that  a single  grain  will  yield  80  millions  of  millions  of  vis- 
ible parts.  The  world  of  organization  furnishes  us  with  still 
more  striking  proofs.  There  exist  animalcules  of  which  it 
would  require  many  millions  to  make  up  the  bulk  of  a com- 
mon grain  of  sand,  yet  these  are  furnished  with  digestive 
and  respiratory  organs,  with  circulating  juices,  and  with 
contrivances  as  elaborate  as  the  mechanism  of  the  highest 
orders  of  life.  How  minute,  then,  must  the  constituent  par- 
ticles be  ! 

All  the  results  of  chemistry  prove  that  the  ultimate  atoms 
of  bodies  are  unehangeable  and  imperishable.  We  can  not 
effect  their  destruction,  or  impress  them  with  new  or  unusual 
qualities,  any  more  than  we  can  call  them  into  existence. 
Those  familiar  instances  in  which  it  appears  that  material 

To  what  extent  can  the  constituent  atoms  be  removed  ? To  what  extent 
can  sulphate  of  indigo  be  divided?  Can  similar  results  be  obtained  from 
metalline  bodies  ? What  evidence  have  we  on  this  point  from  mechanical 
processes  ? What  argument  may  be  drawn  from  the  construction  of  ani 
malcules  ? Are  the  atoms  of  bodies  either  changeable  or  perishable  ? 


6 


PROPERTIES  OF  ATOMS. 


substances  are  destroyed  or  dissipated,  when  properly  under- 
stood, are  only  cases  of  transformation,  or  of  the  origin  of  new 
compounds.  An  atom  once  created  can  by  no  process  be  de- 
stroyed. When,  therefore,  coal  disappears  in  the  act  of  burn- 
ing, it  is  not,  in  reality,  a destruction  of  the  particles  of 
which  the  coal  consists,  but  these  particles,  uniting  with  one 
of  the  constituents  of  the  air,  give  origin  to  a body  of  a dif- 
ferent form,  an  invisible  and  elastic  substance,  from  which, 
however,  the  carbonaceous  particles  could  be  reobtained  by 
resorting  to  proper  methods.  It  is,  moreover,  obvious  that 
the  continuance  and  stability  of  the  universe  itself  depend 
on  the  fact  that  by  no  natural  process  can  material  atoms  be 
cither  created  or  destroyed. 


LECTURE  II. 

Constitution  of  Matter. — Of  the  Interstices  hetween 
Atoms. — They  are  not  casual,  hut  regulated. — Two 
Foi'ces  are  required  to  •produce  this  Result. — Cohesion 
and  Heat. — Proof  that  these  Forces  act  through  very 
limited  Spaces. — Analogy  hetween  the  Structure  of  Mat- 
ter and  the  Structure  of  the  Universe. 

Having,  in  the  preceding  lecture,  established  the  atomic 
constitution  of  matter,  let  us  now  direct  our  attention  to  the 
intervening  interstices. 

4.  The  distances  that  part  the  atoms  of  a 

given  mass  from  one  another  are  not  casual 
or  determined  at  random ; their  magnitude 
is  perfectly  regulated.  Thus,  if  we  take  a 
glass  bulb,  a.  Fig.  4,  with  an  open  neck,  h, 
and  having  filled  the  neck  with  water  to  a 
given  mark,  c,  immerse  its  open  extremity 
in  a glass  of  water,  d,  it  will  be  found  that, 
so  long  as  no  extraneous  cause  intervenes, 
the  water  remains  perfectly  stationary  at 
its  original  point,  c ; but  if,  by  the  appli- 
cation of  a spirit  lamp,  e,  we  raise  the  temperature  of  the 

How  can  the  apparent  destruction  of  bodies  be  explained  ? Are  the  spaces 
between  atoms  regulated  or  at  random  ? What  is  the  experiment,  Fig.  4, 
designed  to  establish  ? 


REGULARITY  OF  INTERSTITIAL  SPACES. 


7 


air  included  in  the  bulb,  it  promptly  dilates ; a dilatation 
which,  however,  does  not  proceed  with  irregularity,  for  the 
volume  of  the  air  steadily  increases  as  the  heat  is  steadily 
continued.  Let  the  lamp  now  be  removed,  and  as  the  tem- 
perature descends,  the  water  comes  back  again  to  its  orig- 
inal point,  because  the  air  recovers  its  original  bulk. 

In  the  same  manner,  if  we  repeat  the  experiment  illus- 
trated in  Fig.  3^  we  shall  see  that  the  bubble  of  air  does  not 
expand  with  irregularity  as  the  pump  is  worked.  It  does 
not  at  one  moment  suddenly  dilate,  and  then  remain  motion- 
less, but  for  each  movement  of  the  pump  it  increases  corre- 
spondingly ; and  as  soon  as  the  pressure  is  restored  to  the 
interior  of  the  machine,  it  shrinks  back  to  its  original  size. 
But  these  expansions  and  contractions  are  the  result  of 
movements  among  the  constituent  atoms,  which  at  one  time 
recede  farther  apart,  and  at  another  come  closer  together. 
It  follows,  therefore,  from  these  considerations,  that  the  dis- 
tances which  separate  the  constituent  atoms  are  not  determ- 
ined by  chance  or  at  random,  but  their  magnitude  is  strictly 
regulated. 

To  produce  these  results  two  forces  are  required  : 1st,  a 
force  of  attraction,  which  continually  tends  to  draw  the 
atoms  closer  together ; 2d,  a force  of  repulsion,  which  tends 
to  remove  them  farther  apart.  The  distance  at  which  they 
are  placed,  at  any  particular  moment,  is  determined  by  the 
balancing  of  these  forces  ; if  the  attractive  force  is  made  to 
increase  in  intensity,  the  particles  approach ; if  the  repuls- 
ive, they  recede. 

Names  have  been  given  to  these  forces,  the  attractive 
force  being  known  under  the  name  of  cohesion ; caloric  or 
heat  appears  to  be  the  principle  of  repulsion. 

All  attractive  and  repulsive  forces  diminish  as  the  dis- 
tances through  which  they  act  increase.  The  attractive 
force  of  the  earth,  the  force  of  gravitation,  is  of  a certain  in- 
tensity on  the  surface  of  our  planet,  but  it  diminishes  as  the 
distances  become  greater.  The  forces  which  connect  to- 
gether the  bodies  of  the  solar  system,  and,  indeed,  one  plan- 
etary system  with  another,  act  through  great  intervals  of 
space.;  thus  the  attractive  force  of  the  sun,  operating  through 


Can  the  same  theory  be  proved  by  resorting  to  other  disturbing  processes  ? 
How  many  forces  are  required  to  account  for  these  facts  ? What  is  their 
nature  ? What  is  the  relation  between  heat  and  repulsion  ? Through  what 
spaces  can  these  forces  operate  ? 


S SIZE  OF  INTEHSTITIAL  SPACES. 

many  millions  of  miles,  retains  the  earth  in  her  orbit.  But 
the  attractive  and  repulsive  forces  which  determine  the  po- 
sition of  the  constituent  atoms  of  bodies  are  limited  to  a very 
minute  space.  If  we  take  two  leaden  bullets,  and  having 
' pared  a small  portion  from  the  surface  of  each,  so  as  to  ex- 
pose a brilliant  metallic  spot,  bring  them  within  an  inch  of 
one  another,  they  exert  no  perceptible  attraction,  and  may 
be  drawn  apart  with  the  utmost  facility ; we  may  diminish 
the  distance  between  them  to  the  tenth,  the  hundredth,  the 
thousandth  part  of  an  inch,  and  still  the  same  observation 
I may  be  made  ; we  may  even  bring  them  in  apparent  con- 
: tact,  and  the  attractive  influence  of  the  particles  of  the  one 
upon  those  of  the  other  is  still  undiscoverable ; but,  on  press- 
ing them  together,  we  can  finally  bring  them  within  the 
range  of  each  other’s  influence,  and  then  they  cohere  to- 
gether as  though  they  were  a single  mass,  and  require  a 
considerable  effort  to  separate  them. 

The  apparatus  figured  in  the  margin  serves  to  illustrate 
the  same  result.  Suspend  a circu- 
lar piece  of  plate  glass,  a,  Fig.  5, 
an  inch  in  diameter,  to  one  of  the 
arms  of  a balance,  b,  c,  counter- 
poising it  on  the  opposite  arm  by 
^ weights  placed  in  the  scale-pan,  d. 
Beneath  the  plate  of  glass  place  a 
cup,  e,  containing  some  quicksilver, 
and  it  can  be  proved  that  so  long  as  the  glass  is  at  a sens- 
ible distance  from  the  surface  of  the  quicksilver,  no  attrac- 
tion between  them  is  exhibited  ; for,  were  such  the  case,  the 
arm  of  the  balance  should  incline,  and  the  glass  descend. 
As  long  as  the  smallest  perceptible  space  intervenes,  no  at- 
tractive action  is  developed  ; but  on  bringing  the  two  sur- 
faces in  contact,  they  cohere ; and  now  it  requires  the  addi- 
tion of  a considerable  weight  in  the  scale-pan  to  draw  them 
asunder.  This  result  does  not  depend  on  the  pressure  of  the 
air,  for  it  equally  takes  place  in  a vacuum. 

From  experiments  of  this  kind,  therefore,  we  gather  that 
the  spaces  through  which  molecular  attractions  and  repul- 
sions can  act  are  very  limited,  and  it  follows  of  necessity 
that  the  interstices  which  separate  the  atoms  of  bodies  are 


Fig.h. 


How  can  this  be  proved  by  leaden  bullets  ? Describe  the  apparatus,  Fig. 
5.  What  is  its  use  ? What  the  fact  which  is  proved  by  it  ? Does  the  ex- 
periment depend  on  the  pressure  of  the  air  ? 


CONSTITUTION  OF  MATTER. 


9 


exceedingly  minute,  for  through  those  spaces  the  action  of 
these  forces  extends.  If  the  limiting  distance  through  which 
molecular  attraction  and  repulsion  ean  reach  is,  as  there  is 
reason  to  believe,  from  some  of  the  experiments  of  Newton, 
less  than  the  millionth  of  an  inch,  v/e  are  entitled  to  con- 
clude that  the  interstitial  spaces  are  much  smaller. 

To  what,  then,  do  these  results  finally  point  in  regard  to 
the  constitution  of  matter,  if,  as  we  have  seen,  the  constit- 
uent atoms  themselves  are  inconceivably  minute,  and  the 
spaces  that  separate  them  as  small  as  we  have  reason  to 
conclude  ? We  may  look  upon  the  universe  as  representing 
on  a grand  scale  the  constitution  of  matter  on  a minute  one. 
The  planetary  bodies  which  compose  the  solar  system,  and 
which  are  held  in  their  orbits  by  the  attraction  of  a central 
mass,  are  separated  from  one  another  by  enormous  spaces, 
to  which  their  own  magnitudes  bear  but  an  insignificant 
proportion.  About  forty  such  bodies,  great  and  small,  com- 
pose the  group  or  family  to  which  our  earth  belongs.  But 
as  there  are  systems  of  opaque  planetary  bodies,  so  also 
there  are  systems  of  self-luminous  suns,  which  compose  to- 
gether colonies  of  stars.  In  the  universe  myriads  of  such 
systems  exist,  separated  from  one  another  by  spaces  so  great 
that  the  mind  can  form  no  just  idea  of  them.  planet, 
such  as  Jupiter  with  its  attendant  satellites  ; a self-lumin- 
ous star,  like  our  sun  with  its  surrounding  bodies  ; a group 
of  shining  stars,  such  as  are  scattered  over  our  skies ; a col- 
lection of  such  groups  as  form  the  nebular  masses ; these, 
in  succession,  furnish  us  with  a series  of  illustrations  on  a 
scale  continually  increasing  in  dimensions  of  the  constitution 
of  matter,  which  is  made  up  of  isolated  atoms  placed  at  va- 
riable distances  from  each  other,  the  size  of  these  atoms 
bearing  an  insignificant  proportion  to  the  spaces  intervening 
between  them. 

The  human  mind  is  so  constituted  th^  it  is  unable  to 
appreciate  whatever  is  exceedingly  great  or  exceedingly 
small.  We  can  neither  attach  a precise  idea  to  the  magni- 
tudes and  grander  relations  of  the  universe,  nor  to  the  atomic 
constitution  of  a grain  of  dust.  Hereafter,  when  we  come 
to  speak  of  the  phenomena  of  light,  we  shall  see  that  by  fol- 
lowing the  same  philosophical  methods  which  have  been 

What  are  the  limiting  distances  through  which  molecular  forces  can  act  ? 
State  the  analogy  between  the  constitution  of  the  universe  and  the  consti- 
tution of  matter. 

A 2 


10 


CONSTI'TUflON  OP  MATTER, 


cultivated  with  such  success  iu  astronomy,  and  which  have 
furnished  us  with  a general  view  of  the  constitution  of  the 
universe,  we  also  can  obtain  a general  view  of  the  scale 
which  has  been  used  in  the  constitution  of  material  bodies, 
a scale  which  brings  before  us  new  ideas  of  time  and  space. 
When  we  are  told  that  in  the  millionth  part  of  a second  a 
wave  of  violet  light  pulsates  or  trembles  seven  hundred  and 
twenty-seven  millions  of  times,  and  that,  if  we  divide  a sin- 
gle inch  into  ten  millions  of  equal  parts,  this  violet  wave  is 
only  one  hundred  and  sixty-seven  of  such  parts  in  length, 
we  obtain  a glimpse  of  the  scale  on  which  material  bodies 
are  composed,  and  must  confess  the  inability  of  the  human 
imagination  to  form  a proper  conception  of  such  results, 
though  we  may  feel  a just  pride  in  the  intellectual  power 
which  has  ascertained  them. 


PART  I. 

THE  FORCES  OF  CHEMISTRY. 


LECTURE  III. 

Heat. — Preliminary  Ideas  of  the  Nature  of  Heat, — In- 
fluence of  Heat  in  the  inorganic  and  organic  Worlds, 
— Modes  of  Transference. — Illustrations  of  Expansion. 
— Heat  determines  the  Magnitude  and  Form  of  Bod- 
ies— Affects  our  Measures  of  Time  and  Space — De- 
termines the  Distribution  of  Animals  and  Plants. 

Writers  on  chemistry  signify  by  the  term  Caloric  the 
agent  which  excites  in  our  bodies  the  sensation  of  heat. 
By  some,  however,  heat  and  caloric  are  used  synonymously. 
Those  who  look  upon  this  force  as  if  it  were  a material  and 
imponderable  substance,  ascribe  to  the  particles  of  caloric  a 
self- repulsive  power,  and  an  attraction  for  the  particles  of 
ponderable  bodies. 

So  great  is  the  control  which  caloric  exercises  over  all 
kinds  of  chemical  changes,  that  few  experiments  can  be 
made  in  which  transformations  of  substances  take  place 
without  contemporaneous  disturbances  of  temperature.  In 
some,  heat  is  evolved  ; in  others,  cold  is  produced.  To  this 
agent,  moreover,  we  so  constantly  resort  for  the  promotion 
of  molecular  changes,  that  the  chemist  has  been  not  inaptly 
designated  the  Philosopher  by  Fire. 

It  is  not  alone  in  the  inorganic  world  that  the  influences 
of  caloric  are  traced.  Life  can  not  take  place  except  with- 
in certain  limits  of  temperature  ; limits  which  are  compre- 
hended between  the  freezing  and  the  boiling  points  of  water, 
that  is,  within  one  hundred  and  eighty  degrees  of  our  ther- 
mometer ; and,  in  point  of  fact,  within  a narrower  range 
than  that.  It  is,  therefore,  not  alone  in  chemistry,  but  also 

What  is  caloric  ? WTiat  is  heat  ? On  the  hypothesis  that  caloric  is  an 
imponderable  substance,  what  are  its  properties  ? Why  is  it  that  the  study 
of  caloric  is  of  such  great  importance  in  chemistry  ? Within  what  limits 
of  temperature  can  living  things  exist 


12 


HEAT  PJIODUCES  EXPANSION. 


in  physiology,  that  the  relations  of  this  agent  are  of  inter- 
est. 

When  an  ignited  mass,  as  a red-hot  hall,  is  placed  in  the 
middle  of  a room,  common  observation  satisfies  us  that  it 
rapidly  loses  its  heat,  its  temperature  descending  until  it 
becomes  the  same  as  that  of  surrounding  walls  and  other 
bodies.  This  loss  is  due  to  several  causes.  A part  of  the 
heat  is  carried  away  by  contact  with  the  body  which  sup- 
ports the  ball,  a part  by  certain  motions  established  in  the 
surrounding  air,  and  a part  by  radiation.  This  removal 
passes  under  the  name  oi transference ; and  as  soon  as  the 
temperature  has  declined  to  that  of  the  adjacent  bodies,  an 
equilibrium  is  said  to  have  been  attained. 

There  are  two  methods  by  which  caloric  can  be  transfer- 
red : 1st.  By  radiation  ; 2d.  By  convection.  Of  the  former 
we  have  two  varieties — general  radiation,  and  interstitial 
radiation. 

Under  the  influence  of  an  increasing  temperature  sub- 
Fig,  6.  stances  expand.  This  takes  place,  whatever  their 
form  may  be,  whether  solid,  liquid,  or  gaseous.  The 
experiment  which  is  illustrated  by  Fig>  1 establishes 
this  fact  in  the  case  of  a copper  ball ; and  that  the 
^ same  law  holds  good  for  liquids,  may  be  proved  by 

J taking  a glass  tufc,  a,  b,  Fig.  6,  open  at  the  extrem- 
^ ity,  a,  but  having  a bulb,  c,  blown  upon  it  at  the 
^ other  end.  The  bulb  and  a part  of  the  tube,  as  high 
as  b,  is  to  be  filled  with  any  liquid  substance,  such 
as  water,  spirits  of  wine,  or  oil ; and  the  heat  of  a 
lamp,  d,  applied.  As  the  liquid  becomes  warm,  it  dilates, 
, ^ as  is  shown  by  its  rising  in  the  tube,  the  dilatation 
increasing  with  the  temperature. 

If  novv^  the  liquid  be  removed  from  the  bulb,  and 
the  tube  be  inverted,  as  shown  in  Fig.  7,  in  a glass 
of  water,  we  can  prove  the  same  fact  for  gaseous  sub- 
stances, taking,  as  the  type  or  representative  of  them, 
atmospheric  air  ; for,  on  simply  grasping  the  bulb,  c, 
. in  the  hand,  the  air  which  is  in  it  dilates  with  the 
' warmth,  and  bubbles  pass  in  succession  from  the  open 
end  of  the  tube  through  the  water  in  the  glass,  d. 

Through  what  causes  does  the  temperature  of  a body  descend  ? What  is 
meant  by  transference  and  by  equilibrium  ? In  how  many  ways  can  caloric 
be  transferred  ? How  many  varieties  of  radiation  are  there  ? By  wliat 
means  can  it  be  proved  that  solids,  liquids,  and  gases  expand  as  their  tern 
perature  rises,  and  contract  as  it  descends  ? 


EFFECTS  OP  HEAT. 


13 


We  conclude,  therefore,  that  solids,  liquids,  and  gases  ex- 
pand as  their  temperature  rises,  and  contract  as  their  tem- 
perature falls. 

The  magnitude  of  all  objects  around  us  is  determined  by 
their  temperatures.  A measure  which  is  a yard?  long  in 
summer  is  less  than  a yard  in  winter  ; a vessel  which  holds 
a gallon  in  winter  will  hold  more  than  a gallon  in  summer. 
And  as  the  degrees  of  heat  vary  not  alone  at  different  sea- 
sons of  the  year,  but  also  during  every  hour  of  the  day,  it  is 
clear  that  the  dimensions  of  all  objects  must  be  undergoing 
continual  changes.  The  appearance  of  stationary  magni- 
tudes which  such  objects  present  is  therefore  altogether  a 
deception. 

Heat  thus  determines  the  size  of  bodies  ; it  also  determ- 
ines their  form.  As  we  have  said,  there  are  three  forms 
of  bodies,  solid,  liquid,  and  gaseous.  A mass  of  ice,  if  ex- 
posed to  a temperature  of  above  32°,  melts  into  water  ; and 
if  that  water  be  raised  to  212°,  it  passes  into  the  form  of 
steam — a gaseous  body.  The  assumption  of  the  solid,  the 
liquid,  or  the  gaseous  condition,  depends  on  the  existing 
temperature. 

In  the  same  manner  that  it  affects  our  measures  of  space, 
caloric  affects  our  measures  of  time.  Clocks  and  watches 
measure  time  by  the  vibrations  of  pendulums,  or  the  oscil- 
lations of  balance  wheels,  the  uniformity  of  the  action  of 
which  depends  on  the  uniformity  of  their  size.  When  the 
temperature  rises,  the  rod  of  a pendulum  lengthens,  and  its 
vibrations  are  made  more  slowly  ; the  clock  to  which  it  is 
attached  loses  time.  When  the  temperature  declines,  the 
pendulum  shortens  ; it  beats  too  quick,  and  the  clock  gains. 
Similar  observations  may  be  made  in  the  case  of  watches. 
To  obviate  these  difficulties  many  contrivances  have  been 
invented,  such  as  the  gridiron  pendulum,  the  compensation 
balance  wheel,  &c.  Advantage  has  also  been  taken  of  such  ^ 
substances  as  expand  but  little  for  a given  elevation  of  tem- 
perature ; and  thus  excellent  clocks  have  been  made,  the 
pendulum  rods  of  which  were  formed  of  a slip  of  marble. 

The  natural,  as  well  as  the  artificial  measures  of  time, 
depend  on  the  influence  of  heat.  Our  unit  of  time  — the 


Is  there  any  variation  at  different  seasons  in  the  length  of  measures  or 
the  capacity  of  vessels  ? What  is  it  that  determines  the  form  of  bodies  ? 
How  can  caloric  affect  our  measures  of  time  ? By  what  contrivances  have 
this  difficulty  been  avoided  ? 


14  CONNECTION  OF  TEMPERATURE  AND  TIME. 

day — is  the  period  which  elapses  during  one  complete  rota- 
tion of  the  earth  on  her  axis.  The  length  of  this  period  is 
determined  by  the  mean  temperature  of  her  mass.  Should 
the  mean  temperature  of  the  whole  earth  fall,  her  magni- 
tude must  become  less,  or,  what  is  the  same  thing,  her  di- 
ameter must  shorten.  It  results  from  very  simple  mechan- 
ical principles,  that  a given  mass,  the  dimensions  of  which 
are  variable,  rotating  on  its  axis,  will  complete  each  rota- 
tion in  a shorter  space  of  time  as  its  diameter  becomes  small 
er.  Thus,  when  we  tie  a weight  to  the  end  of  a thread, 
and,  swinging  it  round  in  the  air,  permit  the  thread  to  wrap 
round  one  of  the  fingers,  as  the  thread  shortens  by  wrapping, 
the  weight  accomplishes  its  revolution  in  a less  period. 
Now,  transferring  this  illustration  to  the  case  before  us,  if 
the  mean  temperature  of  the  earth  had  ever  declined,  she 
must  have  become  less  in  size,  and,  therefore,  turned  round 
quicker,  and  the  length  of  the  day  must  have  necessarily 
been  less.  But  astronomical  observations^  for  a period  of 
more  than  2000  years  back,  prove  conclusively  that  the 
length  of  the  day  has  not  changed  by  so  small  a quantity  as 
the  part  of  a second,  and  we  therefore  are  warranted 
in  inferring  that  the  mean  temperature  of  the  globe  has  not 
perceptibly  fallen. 

The  distribution  of  heat  on  the  surface  of  the  earth  de- 
termines, for  the  most  part,  the  distribution  of  animals  and 
plants ; to  each  climate  its  proper  denizens  are  assigned. 
It  is  this  which  confines  the  lion  to  the  torrid  regions,  and 
the  white  bear  to  the  frigid  zone.  In  the  case  of  man,  who 
has  the  power  of  accommodating  his  diet  and  his  dress  to 
external  requirements,  almost  any  part  of  the  earth  is  hab- 
itable. Plants,  like  the  inferior  animals,  have  their  locali- 
ties determined  chiefly  by  the  influence  of  heat.  It  is  for 
this  reason  that  even  in  tropical  climates,  if  we  ascend  from 
the  foot  to  the  top  of  a very  high  mountain,  we  successively 
pass  through  zones  occupied  by  trees  and  plants  which,  dif- 
fering strikingly  from  one  another,  have  analogies  with  those 
which  occupy  respectively  the  torrid,  the  temperate,  and  the 
frigid  zones,  on  the  general  surface  of  the  earth. 


Do  these  disturbances  affect  the  natural  as  well  as  the  artificial  measures 
of  time  ? How  can  it  be  proved  that  the  mean  temperature  of  the  earth  has 
not  for  many  centuries  changed  ? What  is  it  that  chiefly  determines  the 
distribution  of  plants  and  animals  ? 


EXPANSION  OF  GASES, 


15 


LECTURE  IV. 

Expansion  of  Gases  and  Liquids.  — Rudberg's  Law. — 
Regularity  of  Gaseous  Expansion. — Ascentional  Pow^ 
er  of  expanded  Gas. — Amount  of  Air  contained  in  the 
same  Volume  at  different  Temperatures. — Gas  Ther- 
mometers.  — Expansion  of  Liquids.  — The  Mercury 
Thermometer. 

If  we  compare  together  the  three  forms  of  bodies,  as  re- 
spects their  changes  of  volume  under  the  influence  of  heat, 
we  shall  find  that  for  a given  rise  of  temperature,  gases  ex- 
pand the  most,  liquids  intermediately,  and  solids  least  of 
all.  To  this  rule  but  few  exceptions  are  known ; liquid 
carbonic  acid,  however,  expands  about  four  times  as  much 
as  any  gaseous  body. 

When  heated  from  the  freezing  to  the  boiling  point  of 
water. 


1000  cubic  inches  of  iron  become 1004 

1000  “ “ water  » 1045 

1000  » “ air  “ 1365 


Recent  experiments  have  proved  that  gases  differ  among 
themselves  in  expansibility,  though  the  differences  are  not 
to  any  great  extent.  For  the  permanently  elastic  gases, 
atmospheric  air  may  be  taken  as  the  type  ; the  experiments 
of  Rudberg  show  that  it  expax.ds  of  its  volume  at  32° 
for  every  degree  of  Fahrenheit’s  thermometer.  As  the  same 
quantity  of  gas  occupies  very  different  volumes  at  different 
temperatures,  it  is  necessary,  in  this  and  other  such  cases, 
to  state  some  specific  temperature  at  which  the  estimate  of 
its  volume  is  made  ; the  same  gaseous  mass  occupies  a much 
greater  space  at  75°  than  it  does  at  32°.  In  the  instance 
before  us,  we  consider  the  original  volume  to  be  that  which 
the  gas  would  have  at  32°,  and,  as  has  been  said,  eveiy  de- 
gree above  that  point  will  increase  the  volume  by  of 
the  bulk  it  then  possessed. 

Gases  expand  with  uniformity  as  their  temperature  in- 

Of  solids,  liquids,  and  gases,  which  expand  most  by  heat  ? In  what  re- 
spect is  liquid  carbonic  acid  peculiar  ? Is  there  any  diiference  among  gases 
in  their  rates  of  expansion  ? What  is  Rudberg’s  estimate  of  the  amount  of 
expansion  of  air?  Why  are  we  required  in  these  cases  to  adopt  a specific 
temperature  ? Do  gases  expand  uniformly  ? 


in  EXPANSION  OP  GASES. 

creases.  Ten  degrees  of  heat  produce  the  same  relative  ef- ' 
feet,  whether  applied  at  a low  or  at  a high  temperature  ; 
this  regularity  probably  arises  from  the  want  of  cohesion 
which  the  gaseous  particles  exhibit;  as  we  shall. presently 
see,  it  is  not  observed  in  the  case  of  liquids  and  solids. 

The  change  in  specific  gravity  of  atmospheric  air,  when  it 
Fig.  8.  is  warmed,  is  one  of  the  causes  of  the  rise 

of  Montgolfier  balloons.  These,  which 
were  invented  in  France  in  the  year  1782, 
consist  of  a bag  or  globe  of  light  materi- 
als, such  as  paper  or  silk,  with  an  aper- 
ture at  the  lower  part,  through  which, 
by  the  aid  of  combustible  material,  as 
straw  or  shavings,  the  air  in  the  interior 
may  be  rarefied.  On  a small  scale,  they 
may  be  made  of  thin  tissue  paper,  pasted 
together  so  as  to  form  a sphere  of  two  or  three  feet  in  diam- 
eter, an  aperture  being  cut  in  the  lower  portion  six  inches 
or  more  in  width,  and  beneath  it  a piece  of  sponge,  soaked 
in  spirits  of  wine,  suspended.  This  being  set  on  fire,  the 
flame  rarefies  the  air  in  the  interior  of  the  balloon,  which, 
though  it  might  be  at  first  flaccid,  soon  dilates,  and  the 
whole  apparatus  will  now  rise  in  the  air,  precisely  on  the 
same  principle  that  a cork  rises  from  the  bottom  of  a vessel 
of  water-. 

There  is,  however,  another  cause  in  operation  in  this  case. 
The  combustible  material  commonly  employed  gives  rise 
(luring  its  burning  to  the  disengagement  of  the  vapor  of  wa- 
ter— -steam,  which  is  much  lighter  than  air.  In  the  oper- 
ation of  cupping,  the  glass  receives  for  a moment  the  flame 
of  a spirit  lamp,  and  is  then  quickly  applied  to  the  surface 
of  the  skin  ; the  vapor  of  water  quickly  condensing,  and  the 
heated  air  contracting,  a very  good  vacuum  can  be  made. 

From  the  circumstance  that  the  volume  of  air  changes 
so  readily  with  changes  of  temperature,  contracting  under 
the  influence  of  cold,  and  dilating  under  that  of  heat,  it  is 
plain  that  in  different  climates  on  the  earth’s  surface  a very 
different  amount  of  atmospheric  air  is  included  under  the 
same  measure.  A vessel  which  will  hold  precisely  one  ounce 
weight  at  the  mean  temperature  of  New  York,  will  hold 
more  than  an  ounce  in  the  cold  polar  regions,  and  less  than 

are  Montgolfier  balloons,  and  why  do  they  rise?  Why  is  it  that 
ilio  \vr‘i;>1it  of  nir  in  a given  measure  is  different  at  different:  places? 


GAS  THERMOMETERS. 


17 


an  ounce  in  the  tropics.  In  the  former  situation  the  air  is 
more  dense,  because  it  is  in  a contracted  condition  by  reason 
of  the  low  temperature,  and  therefore  a greater  weight  is 
included  under  a given  volume  ; in  the  latter,  the  reverse  is 
!the  case.  These  facts  are  supposed  to  be  connected  with 
' certain  physiological  results,  as  we  shall  hereafter  see. 

The  expansions  of  atmospheric  air  taking  place  with  reg- 
ularity as  the  temperature  rises,  that  substance  is  occasion- 
ally employed  as  a means  of  thermometric  admeasurement. 
The  air  thermometer,  called  also  Sanctorio’s  thermometer, 
but  which  was  invented  by  Galileo  about  1603,  consists  of 
a tube  of  glass,  a.  Fig.  9,  terminated  at  its  upper  ^ 
extremity  by  a bulb,  b ; the  other  end  of  the  tube  ^ ^ 
being  open,  dips  beneath  the  surface  of  some  col-  ^ 
oYcd  water  in  a cup  or  reservoir,  c,  which  serves 
also  as  a foot  or  support  to  the  instrument.  The 
bulb  and  part  of  the  tube  are  full  of  air ; the  re- 
mainder of  the  tube  is  occupied  by  the  colored  wa- 
ter, which,  by  its  movements  up  and  down,  serves  to 
: indicate  changes  in  the  volume  of  the  included  air. 

To  the  side  of  the  tube  a scale  of  divisions  is  affixed, 
and  the  tube  is  not  arranged  so  tightly  in  the  neck 
of  the  reservoir  but  that  there  is  a free  passage  for  “ 
the  air  in  and  out  of  that  part  of  the  instrument.  On  touch- 
ing the  ball  with  the  lingers,  the  air  within  it  becomes 
warm,  dilates,  and  depresses  the  liquid  in  the  tube,  or,  on 
touching  it  with  any  cold  body,  it  contracts,  and  the  liquid 
rises. 

This  form  of  thermometer  is  liable  to  a difficulty  which 
renders  it  impossible  to  rely  upon  its  indica-  lo. 

tions,  except  under  particular  circumstances. 

It  is  affected  by  variations  of  atmospheric  press- 
ure as  well  as  by  changes  of  heat.  To  prove 
that  this  is  the  case,  place  such  a thermometer 
under  the'  receiver  of  an  air  pump,  as  shown  in 
Fig.  10  ; on- producing  the  slightest  degree  of 
rarefaction,  the  liquid  in  the  tube  is  instantly 
depressed,  and  on  restoring  the  pressure  of  the 
air,  it  returns  to  its  original  position. 


Describe  the  thermometer  of  Sanctorio,  By  whom  w-as  it  really  invent^ 
ed  ? How  can  the  use  of  this  instrument  be  illustrated  ? By  what  dis- 
turbing cause  IS  Sanctorio’s  thermometer  affected?  How  may  that  bo 
proved  ? v._ 


18 


EXPANSION  OF  LIOUIDS. 


The  difFerential  thermometer  is  a gas  thermometer,  so 
Fig,  11.  arranged  as  to  he  free  from  the 

foregoing  difficulty.  It  consists 
of  a glass  tube,  a h,  Fig.  11,  bent 
[]  into  the  form  represented  in  the 
b figure,  with  a bulb  blown  on  each 
extremity.  To  the  horizontal  part 
a scale  of  divisions  is  affixed.  The 
bulbs  are  full  of  atmospheric  air, 
and  in  the  tube  there  is  a small  column  of  colored  liquid, 
which  serves  by  its  movements  as  an  index.  To  under- 
stand the  action  of  this  instrument,  it  is  only  necessary  tu 
consider  what  will  take  place  when  it  is  carried  into  a room 
the  temperature  of  which  is  very  high  of  very  low.  If  the 
former,  the  air  in  both  bulbs,  becoming  equally  warm,  will 
expand  in  both  equally,  and  the  column  of  fluid  which  acts 
as  an  index  being  pressed  equally  in  opposite  directions,  does 
not  move  at  all.  If  the  latter,  the  air  in  both  bulbs  cool- 
ing equally,  contracts  equally,  and  again  no  movement  en- 
sues. It  is  immaterial,  therefore,  whether  we  warm  or  cool 
both  bulbs,  the  instrument  is  motionless.  But  if  one  of  the 
bulbs,  c,  is  made  warmer  than  the  other,  d,  movement  at 
once  ensues  in  the  liquid  column  from  c toward  d.  Move- 
ment of  the  index,  therefore,  takes  place  when  the  bulbs  are 
at  different  temperatures,  and  hence  the  instrument  is  called 
a differential  thermometer.  It  was  formerly  of  considera- 
ble use  in  researches  connected  with  radiant  heat. 

Different  liquids  expand  differently  for  the  same  thermo- 
metric disturbance.  This  is  easily 
shown  by  an  apparatus,  as  Fig.  12, 
in  which  we  have  three  tubes,  a,  b,  c, 
with  bulbs  on  their  ends,  dipping  into 
a trough,  /,  of  tin  plate.  The  tubes 
and  bulbs  should  be  all  of  the  same 
size,  and  filled  with  the  liquids  to  be 
tried  to  the  same  height.  To  each  a 
scale  is  annexed.  Let  a be  filled  with 
quicksilver,  h with  water,  and  c with  alcohol ; on  pouring 
hot  water  into  the  trough,  two  phenomena  are  witnessed  : 

Describe  the  differential  thermometer.  If  this  instrument  be  carried  into 
a warm  and  then  into  a cold  room,  does  its  index  move  ? Wliy  is  it  called 
differential  thermometer?  How  can  it  be  shown  that  different  luiuids  ex- 
pand differently  ? 


Fig.  12. 


TUP.  MERCURIAL  THERMOMETER. 


19 


1st  All  the  liquids  expand  ; 2d.  They  expand  unequally 
when  compared  together,  the  mercury  expanding  least,  the 
water  intermediately,  and  the  alcohol  most. 

On  being  heated  from  the  freezing  to  the  boiling  point  ot 

water, 

Alcohol  expands  1 part  in 9 

Oil  “ 1 “ A 

Water  “ 1 “ 22  TO 

Mercury  “ 1 “ 55  50 

Liquids  which  have  arisen  from  the  condensation  of  such 
gases  as  cyanogen,  sulphurous  acid,  and  especially  carbonic 
acid,  are  among  the  most  expansible  bodies  known,  ihus 
liquid  carbonic  acid,  warmed  from  32°  to  86°,  expands  four 

times  as  much  as  atmospheric  air. 

In  the  case  of  several  groups  of  liquids,  as  alcohol,  sul- 
phuret  of  carbon,  and  wood  spirit,  it  has  been  found  that 
the  rate  of  expansion  is  precisely  the  same  if  estimated  at 
equal  distances  from  their  several  boiling  points.  jr/^.13. 

Unlike  gases,  all  liquids  expand  irregularly  as 
their  temperature  rises,  a given  amount  of  heat  pro- 
ducing a much  greater  effect  at  a high  than  at  a 
low  temperature.  Ten  degrees  of  heat,  applied  to 
a given  liquid  at  20 0"^,  will  produce  a greater  ex- 
pansion than  if  applied  at  100^.  The  reason  ap- 
pears to  be,  that  as  a liquid  dilates  its  cohesive 
force  becomes  less,  because  its  particles  are  being 
removed  farther  from  each  other , and,  as  the  co- 
hesive force  weakens,  its  antagonistic  power,  the 
heat,  produces  a greater  effect. 

Advantage  is  taken  of  the  properties  of  liquids 
in  the  making  of  thermometers.  For  these  pur- 
poses, alcohol  and  mercury  are  the  fluids  selected. 

The  mercurial  thermometer  consists  of  a fine  cap- 
illary tube,  Fig.  13,  with  a bulb  blown  on  one 
end  ; the  bulb  and  part  of  the  tube  are  to  be  fill- 
ed with  quicksilver,  and  the  air  expelled  from  the 
rest  of  the  tube  by  warming  the  bulb  until  the 
metal  rises  by  expansion  to  the  top  of  the  tube,  and 
at  that  moment  hermetically  sealing  the  glass  by 

Of  mercury,  water,  and  alcohol,  what  is  the  order  of  expansion  ? Do 
liquids,  like  gases,  expand  with  regularity?  What  is  the  cause  of  ^if. 
ference  ? For  making  thermometers,  what  liquids  are  selected  , rlow  is 
the  mercurial  thermometer  made  ? 


20 


THE  MERCURIAL  THERMOMETER. 


melting  tlie  end  of  it  with  a blow-pipe.  As  the  thermom- 
eter cools,  the  quicksilver  retreats  from  the  top  of  the  tube, 
and  leaves  a vacuum  above  it. 

It  remains  now  to  annex  such  a scale  to  the  instrument 
as  may  make  its  indications  comparable  with  other  instru- 
ments. To  effect  this,  the  thermometer  is  plunged  into  a 
vessel  containing  melting  ice  or  snow,  and  opposite  the  point 
at  which  the  quicksilver  stands  is  marked  32°.  It  is  then 
transferred  to  another  vessel  in  which  water  is  rapidly  boil- 
ing, and  the  point  opposite  which  it  then  stands  is  marked 
212°.  The  intervening  space  is  divided  into  180  equal 
parts  ; these  are  degrees,  and  similar  divisions  are  made  on 
the  scale  for  all  points  above  212°  and  below  32°.  The 
zero  point,  or  cipher  of  the  scale,  is  therefore  32  degrees  be- 
low the  freezing  point  of  water. 

It  has  been  observed,  that  in  the  course  of  time  the  freez- 
ing point  of  some  thermometers  changes.  This  is  due  to 
the  pressure  of  the  air  acting  on  the  bulb,  the  thin  glass  of 
which  yields  to  a certain  extent,  and  the  liquid  consequent- 
ly rises  in  the  tube.  The  same  effect  will  often  take  place 
instantaneously  by  exposing  a thermometer  to  a high  tem- 
perature. It  is  therefore  necessary  to  verify  from  time  to 
time  the  graduations  of  these  instruments. 

The  zero  point  of  the  thermometric  scale  is  not  to  be  re- 
garded as  indicating  the  total  absence  of  heat.  Observa- 
tions have  been  made  in  cold  climates  of  degrees  almost  80° 
below  0 ; and  by  the  aid  of  liquefied  protoxide  of  nitrogen, 
— 220°  has  been  reached... 

The  melting  of  ice  and  the  boiling  of  water  are  the  fixed 
thermometric  points.  They  have  been  selected  for  the  pur- 
pose of  rendering  thermometers  comparable  with  each  other. 
The  numbers  which  are  attached  to  these  points  are  arbi- 
trary, and  accordingly  three  different  scales  have  been  in- 
troduced in  different  countries.  That  which  is  commonly 
used  in  America  and  England  is  the  Fahrenheit  scale,  which, 
as  we  h^ave  just  seen,  makes  the  melting  point  of  Ice  32°, 
and  the  boiling  of  water  212°.  In  France,  the  Centigrade 
scale  is  employed  ; this  has  for  the  melting  of  ice  0°,  and 
for  the  boiling  of  water  100°.  In  some  parts  of  Europe, 

Is  there  a vacuum  above  the  mercury  in  the  tube  ? How  is  the  scale  ad- 
justed ? What  is  the  freezing  and  what  the  boiling  point  ? What  is  meant 
by  the  zero  ? What  are  the  fixed  points  ? Why  are  these  fixed  points  em 
ployed  ? What  three  scales  have  been  introduced  ? What  is  the  Centi 
grade  icale? 


THE  MERCURIAL  THERMOMETER. 


21 


Reaumur’s  scale  is  used,  the  points  of  which  are  respective 
ly  0^  and  80°.  Chemical  authors  always  specify  the  ther 
mometer  they  use  by  a letter  attached  to  the  numbers ; 
thus,  212F.,  100  0.,80  R.,  refer  to  the  boiling  of  water  on 
Fahrenheit’s,  the  Centigrade,  and  Reaumur’s  scales.  It  is 
obvious  that  these  degrees  are  readily  convertible  into  each 
other  by  a simple  arithmetical  process. 


LECTURE  V. 

Expansion  of  Liquids  and  Solids. — Importance  of  the 
Thermometer. — Alcohol  Thermometer. — Point  of  Max- 
imum Density  of  Diquids. — Maximmn  Density  of  Wa- 
ter connected  with  Duration  of  the  Seasons. — Expan- 
sion of  Solids. 

From  the  considerations  advanced  in  Lecture  III.,  we  can 
perceive  the  importance  of  the  thermometer.  As  all  our 
measures  of  space  and  time  are  affected  by  variations  of 
temperature,  the  thermometer,  which  measures  those  vari- 
ations, must  necessarily  be  one  of  the  fundamental  instru- 
ments of  physical  science.  If  we  state  that  a given  object 
is  a foot  long,  we  must  specify  the  temperature  at  which 
the  measure  was  taken,  for  at  a lower  temperature  it  will 
be  less  than  a foot,  and  at  a higher  it  will  be  more. 

There  are  several  peculiarities  which  quicksilver  possesses 
that  eminently  fit  it  to  be  a thermometric  fluid.  1st.  It  can 
always  be  obtained  in  a state  of  uniform  purity.  2d.  It  ex- 
pands with  greater  regularity  than  most  liquids,  as  its  tem- 
perature rises,  and  when  included  in  a bulb  of  glass,  as  in 
the  common  instrument,  the  irregularity  of  expansion  of  the 
glass  almost  exactly  compensates  the  irregular  expansion 
of  the  quicksilver,  and  hence  the  true  temperature  is  very 
accurately  marked.  3d.  The  range  of  temperature  between 
the  points  of  solidification  and  boiling  is  great,  the  former 
being  — 39°  Fahrenheit,  and  the  latter  at  662°  Fahren- 
heit ; that  is,  about  seven  hundred  degrees.  4th.  It  does 
not  soil  or  moisten  the  tube  in  which  it  is  contained,  nor 

Wliat  is  Reaumur’s  ? Can  these  be  converted  into  cacli  oi  her  ? Wliy  is  the 
thermometer  such  an  important  instrument  ? What  are  the  qualities  which 
quicksilver  possesses  which  fit  it  for  these  uses  ? 


22 


MAXIMUM  DENSITY  OF  WATER. 


does  it  adhere  thereto,  but  moves  up  and  down  with  facility. 
5th.  It  is  affected  much  more  readily  than  water  or  spirits 
of  wine  by  a given  amount  of  heat,  as  we  shall  see  when 
we  come  to  speak  of  the  capacity  of  bodies  for  caloric. 

When  very  low  temperatures  have  to  be  measured,  such 
as  approach  or  are  below  the  freezing  point  of  quicksilver, 
we  resort  to  thermometers  filled  with  alcohol,  tinged  with 
some  coloring  matter  to  make  its  movements  visible.  This 
fluid  requires  a diminution  of  temperature  of  more  than  180° 
below  the  zero  of  our  scale  before  it  solidifies,  and  hence  is 
adapted  to  the  measurement  of  low  temperatures. 

If  we  take  some  water  at  100°  Fahrenheit,  and,  placing 
it  in  a vessel  in  which  we  can  observe  its  volume,  reduce 
its  temperature,  we  shall  find,  agreeably  to  the  general  law 
heretofore  given,  that  as  it  cools  it  contracts.  As  it  success- 
ively passes  through  80,  60,  50  degrees,  it  exhibits  a con- 
tinuous diminution  ; but  as  soon  as  it  has  fallen  below  39°, 
although  it  may  still  be  cooling,  it  begins  to  expand,  and 
continues  to  do  so  until  it  reaches  32°,  when  it  freezes.  If 
we  take  some  water  at  32°  and  warm  it,  instead  of  expand- 
ing, it  contracts,  until  it  reaches  39°  ; but  from  that  point, 
any  farther  elevation  of  temperature  causes  it  to  obey  the 
general  law,  and  it  expands. 

It  is  obvious,  therefore,  that  if  we  take  water  at  39°,  it 
is  immaterial  whether  we  warm  it  or  cool  it,  it  will  expand. 
At  that  temperature,  therefore,  this  liquid  occupies  the 
smallest  bulk,  and  is  at  its  greatest  density,  for  neither  by 
cooling  nor  warming  can  we  reduce  it  to  smaller  dimensions. 
The  particular  thermometric  point  at  which  this  takes 
place  is  designated  the  point  of  maximum  density  of  wa- 
ter f and  very  exact  experiments  show  that  it  is  about  39|° 
Fahrenheit. 

There  are  many  liquids  which  thus  have  points  of  max 
imum  density,  and  which  expand  previous  to  assuming  th( 
solid  form.  In  the  act  of  solidifying,  water  undergoes  a ver^ 
great  dilatation,  amounting  to  about  |-th  of  its  volume  ; thfj 
is  the  reason  that  ice  floats  upon  it.  Several  melted  metals 
exhibit  the  same  phenomenon,  and  advantage  is  taken  of 

Under  what  circumstances  are  alcohol  thermometers  used  ? Does  crater 
contract  regularly  when  cooled  from  10Q°  to  32°  ? Does  it  reguh  .ly  ex- 
pand when  warmed  from  32°  ? At  what  thermometric  point  does  tha'  change 
take  place  ? What  is  the  designation  given  to  that  point  ? VV  b ^ is  that 
designation  appropriate  ? Are  there  other  liquids  which  have  ./oints  of 
maximum  density  ? 


POINTS  OF  MAXIMUM  DENSITY. 


23 


the  fact  in  the  arts.  The  alloy  of  which  printers’  types  arc 
formed,  or  stereotype  plates  cast,  in  the  act  of  solidifying, 
expands,  and  hence  forces  itself  into  every  part  of  a mould 
in  which  it  may  he  poured,  and  copies  it  perfectly  ; the 
same  is  the  case  with  melted  cast  iron.  But  it  is  impopi- 
hle  to  obtain  good  castings  with  such  a metal  as  lead,  which 
contracts  as  it  cools,  and  therefore  tends  to  separate  from  the 
surface  of  the  mould,  or  to  leave  vacant  spaces  in  it. 

The  fact  that  water  possesses  a point  of  maximum  dens- 
ity is  connected,  to  a great  extent,  with  several  remarkable 
natural  phenomena ; the  freezing  of  water  on  its  surface  is 
one  of  these  results.  If  the  water  contracted  as  it  cooled, 
the  colder  portions  would  descend,  and  rivers  or  ponds  would 
commence  to  freeze  at  the  bottom  first,  the  solidification  ad- 
vancing steadily  upward.  Such  collections  of  this  liquid 
would,  during  the  course  of  a winter,  become  solid  masses 
of  ice,  and  they  would  greatly  prolong  that  season  of  the 
year,  from  the  length  of  time  required  to  thaw  them.  But 
with  things  as  they  at  present  exist,  the  coldest  water  is  the 
lightest ; it  floats  on  the  warm  water  below  ; solidification 
takes  place  on  the  surface,  and  a veil  or  screen  is  soon  form- 
ed which  protects  the  liquid  beneath.  When  the  warm 
weather  of  spring  comes  on,  the  ice  on  the  surface  is  in  the 
most  favorable  position  for  melting,  and  thus  the  point  of 
maximum  density  of  water  comes  to  be  connected  with  the 
duration  of  the  seasons. 

If  salt  is  added  to  water,  the  point  of  maximum  density 
descends,  until,  when  the  quantity  is  sufficiently  great,  it 
sinks  below  the  freezing  point.  The  observations  just  made 
apply  therefore  only  to  fresh,  and  not  to  salt  water. 

We  have  already  proved  by  the  instrument  represented 
in  Fig.  1,  that  solid  substances  dilate  ^ig.  14. 

as  their  temperature  rises.  The  same 

results  may  be  made  very  apparent  [\^c  

by  the  apparatus.  Fig.  14.  Upon  a ^ 
strong  basis  or  wooden  board,  a,  b,  let  there  be  fastened  two 
brass  uprights,  c with  notches  cut  in  them,  so  as  to  re- 
ceive the  ends  of  the  metallic  bar,  e.  This  bar  should  be 
very  slightly  shorter  than  the  distance  between  the  two  up- 

What  advantage  is  taken  of  this  fact  in  the  arts  ? Why  does  water 
freeze  first  on  its  surface?  How  is  it  that  these  facts  are  connected  with 
the  duration  of  the  seasons  ? How  does  the  instrument.  Fig,  14,  prove  that 
a metallic  bar  expands  when  heated  ? 


24 


EXPANSION  OF  SOLIDS. 


rights,  that  when  it  is  placed  resting  in  their  grooves,  if  we 
take  hold  of  it  and  move  it,  it  will  make  a rattling  sound 
as  we  push  it  backward  and  forward.  If  now  wc  pour  hot 
water  upon  the  bar,  it  dilates,  as  is  proved  on  restoring  it  to 
its  position  between  the  uprights ; it  will  no  longer  rattle, 
for  it  occupies  the  whole  distance  between  them,  and  per- 
haps there  may  even  be  a difficulty  in  forcing  it  into  the 
grooves. 

For  the  determination  of  very  small  spaces,  the  sense  of 
hearing  may  often  be  far  more  effectually  employed  than 
the  sense  of  sight. 

The  pyrometer,  of  which  we  have  several  varieties,  is 

represented  in  Fig. 
15.  It  may  serve 
to  illustrate  the  fact 
that  solid  substan- 
ces expand  by  heat. 
It  consists  essen- 
tially of  a metallic 
bar,  a a,  resting  at 
one  end  against  an 
immovable  prop,  e, 
the  other  end  bear- 
ing upon  a lever,  h. 
The  extremity  of 
this  lever  presses  upon  a second  lever,  c,  which  also  serves 
as  an  index.  Upon  the  index-lever  a spring  acts  so  as  to 
oppose  the  lever  5,  and  the  point  of  the  index  ranges  over  a 
graduated  scale. 

If  now  lamps  be  applied  to  the  bar,  it  expands,  and  the 
pressure  taking  effect  on  the  lever,  puts  it  in  motion,  the 
index  traversing  over  the  scale.  On  removing  the  lamp  the 
bar  contracts,  and  the  spring,  pressing  the  lever  in  the  op- 
posite direction  as  soon  as  the  bar  is  cold,  brings  the  index 
back  to  its  original  point. 


Describe  the  pyrometer  and  the  mode  of  using  it. 


CONTRACTION  AND  DILATATION  OF  SOIilDS.  ^25 


LECTURE  VI. 

Expansion  of  Solids. — Contraction  of  Solids. — They  ex- 
pand irregidarly. — Different  Solids  expand* different- 
ly. — Points  of  Maximum  Density.  — Metallic  Ther- 
mometers.— Nature  of  Thermometric  Indications. 

It  is  a popular  error,  that  when  solid  bodies  have  been 
heated,  they  do  not  return,  on  cooling,  to  their  original  size. 
Without  resorting  to  any  experimental  proof,  a few  simple 
considerations  will  satisfy  us  on  this  point.  If  a bar  of 
metal  be  exposed  for  a length  of  time  in  the  open  air,  it 
will  of  course  be  subjected  to  continual  changes  of  temper- 
ature ; whenever  the  sun  shines  on  it  it  will  expand,  and 
during  the  cold  night  it  will  contract.  If  now,  on  cooling, 
it  did  not  rigorously  come  back  to  its  original  size,  but  re- 
mained a little  elongated,  we  should  observe  it  increasing 
from  day  to  day,  and  no  matter  how  minute  the  difference 
might  be,  in  the  course  of  time  it  would  become  perceptible. 
Public  edifices  in  cities  are  often  surrounded  by  railings  of 
cast  iron,  which  are  constantly  exposed  for  years  to  varia- 
tions of  heat  and  cold,  but  did  any  person  ever  observe  them 
to  grow  or  increase  in  size  ? We  conclude,  therefore,  that 
solid  bodies,  on  coohng  to  their  original  temperature,  regain 
their  original  bulk. 

By  linear  dilatation  we  mean  increase  in  one  dimension, 
as  in  length ; by  cubic  dilatation,  increase  in  all  dimensions, 
length,  breadth,  and  thickness.  Knowing  the  amount  of 
linear  dilatation  of  a given  solid,  we  can  easily  ascertain  its 
cubic  dilatation,  by  multiplying  the  former  by  3.  This  re- 
sult is  near  enough  for  practical  purposes. 

Solids  expand  increasingly  as  their  temperature  rises,  a 
phenomenon  already  observed  in  the  case  of  liquids,  and  due 
to  the  same  cause — a diminution  of  the  cohesive  force  of  the 
particles,  because  of  their  increased  distance. 

Compared  with  one  another,  different  solid  substances  ex- 
pand differently  for  the  same  disturbance  of  temperature. 

What  decisi  ve  proof  can  ])c  given  that  solids,  on  cooling  to  their  original 
temperature,  come  back  to  their  original  size  ? Wliat  is  linear  dilatation? 
What  is  cubic  dilatation  ? How  can  the  former  bo  converted  into  the  lat- 
ter ? Does  the  same  solid  expand  uniformly  or  increasingly  os  its  temper- 
ature rises  ? 


B 


26^ 


COMPENSATION  BAKSr 


This  may  be  shown  by  having  bars  of  difierent  metals,  but 
of  precisely  the  same  lengths,  adjusted  to  the  grooves  of  the 
instrument,  Fig.  14.  If  a bar  of  brass  and  one  of  iron  be 
compared,  it  will  be  found  that  the  brass  expands  more  than 
the  iron,  for  it  will  entirely  fill  the  distance  between  the 
uprights,  while  the  iron  rattles  between  them. 

This  difference  of  expansion  is  also  shown  when  two  long 


common  temperatures  the  compound  bar  is  adjusted  so  as 
to  be  straight,  but  if  hot  water  be  poured  upon  it,  it  imme- 
diately curves,  as  represented  at  a c,  the  strip  of  brass  be- 
ing on  the  outside  of  the  curve  ; if,  on  the  other  hand,  it  be 
■ artificially  cooled,  the  curvature  is  in  the  other  direction,  as 
at  b dy  the  iron  being  on  the  outside  of  the  curve.  All  this 
is  obviously  due  to  the  fact  that,  for  the  same  disturbance 
of  temperature,  the  brass  contracts  and  dilates  much  more 
than  the  iron.  When  the  temperature  is  raised,  the  brass 
becomes  the  longer,  and  compels  the  compound  bar  to  curve, 
it  occupying  the  greater  length  of  the  curve.  When  the 
temperature  falls,  the  brass  becomes  the  shorter,  and  the 
bar  curves  in  the  opposite  direction. 

By  taking  advantage  of  these  metallic  combinations,  pen- 
dulums and  balance-wheels  for  the  accurate  measurement 
of  time  have  been  constructed.  The  gridiron  pendulum  and 
the  compensation  balance  are  examples. 

The  following  table  exhibits  the  expansion  of  various  solid 
substances  when  heated  from  the  freezing  to  the  boiling 
point  of  water : 


Zinc  (cast)  . , 

. 1 in  323 

Gold  . . . 

. 1 in 

682 

Lead  .... 

. 1 “ 351 

Iron  (wire) 

. 1 “ 

812 

Tin  .... 

. 1 “ 516 

Palladium  . . 

. 1 “ 

1000 

Silver  . . . 

. 1 “ 524 

Platinum  . . 

. 1 “ 

1167 

Copper  . . . 

. 1 “ 581 

Flint  glass 

. 1 “ 

1248 

Brass  .... 

. 1 “ 584 

Black  marble  . 

. 1 “ 

2883 

Ice  is  much  more  expansible  than  the  metals,  surpassing. 


Fig.  16. 


slips  of  metal  are  soldered  to- 
S gether  face  to  face.  If  we  fasten 
‘a  in  this  manner  a slip  of  brass  to 


a similar  slip  of  iron,  as  in  Fig. 


d 16,  in  which  a a is  the  slip  of 
iron  and  h b the  slip  of  brass,  at 


Do  different  solids  expand  alike  ? Of  brass  and  iron,  which  expands  most  ? 
Describe  the  construction  of  a compound  bar,  and  the  effect  of  warming 
and  cooling  it.  What  instruments  are  constructed  on  this  property  ? 


METALLIC  THERMOMETERS. 


27 


in  this  respect  zinc.  Glass  and  platinum  can  be  cemented 
together  without  parting  as  they  cool,  for  their  rates  of  ex- 
pansion are  nearly  alike.  The  process  of  cutting  glass  by 
means  of  a hot  rod  depends  on  unequal  expansion. 

Though  a solid  substance  is  usually  regarded  as  expand- 
ing equally  in  any  direction,  this  is  not  always  the  case.  In 
crystals,  of  which  all  the  sides  and  angles  are  not  alike,  there 
may  be  a very  different  rate  of  expansion  in  different  direc- 
tions, and  it  has  even  been  observed  that  they  may  contract 
in  one  direction  while  they  are  expanding  in  another.  The 
figure  of  a crystal  of  carbonate  of  lime  is  for  these  reasons 
different  at  the  freezing  and  the  boiling  point  of  water. 

There  are  some  metallic  bodies  which  exhibit  points  of 
maximum  density  in  the  solid  state.  Rose’s  fusible  metal 
is  an  example.  When  heated  from  32°  to  111°,  it  ex- 
pands, but  after  that  point  it  contracts,  and  continues  to  do 
so  until  it  reaches  156°,  at  which  temperature  it  is  actually 
less  than  it  is  at  32°.  From  this  point  it  again  expands, 
and  continues  to  do  so  until  it  melts,  which  takes  place  at 
about  201°  Fahrenheit. 

Liquid  thermometers  have  a limited  range  of  indication. 
They  can  not  be  exposed  to  degrees  of  heat  approaching  the 
point  of  solidification,  for  then  their  movements  become  ir- 
regular ; neither  can  they  be  used  for  degrees  near  their 
boiling  point,  for  if  vapor  should  form,  the  instrument  would 
be  destroyed.  But  as  there  are  many  metals  which  require 
a very  great  degree  of  heat  to  melt  them,  it  might  be  ex- 
pected that  we  should  find  among  this  class  bodies  well 
suited  for  thermometric  purposes.  The  instrument  given  in 
Fig.  1 5 serves  to  illustrate  such  an  apparatus,  and  also  the 
difficulties  encountered  in  its  use.  From  the  small  extent 
to  which  metals  expand,  this  form  of  instrument  requires 
levers,  or  wheels,  or  some  multiplying  machinery  connected 
with  it,  to  make  the  changes  more  perceptible ; but  such 
mechanical  contrivances  can  not  be  employed  without  the 
introduction  of  certain  causes  of  disturbance.  Friction  oc- 
curs on  the  centres  of  motion,  the  teeth  of  the  wheels  play 
on  each  other,  and  therefore  the  index,  instead  of  moving 
with  regularity  and  precision  as  the  expanding  bar  presses, 
moves  by  starts  often  of  several  degrees  at  a time,  then  it 

What  are  the  properties  exhibited  by  Rose’s  fusible  metal  ? Why  can 
not  liquid  thermometers  be  used  for  very  low  and  very  high  temperatures  ? 
What  difficulties  occur  in  the  use  of  this  instrument  ? 


28 


METALLIC  THERMOMETERS. 


pauses,  and  once  more  starts  again,  the  whole  movement 
being  incompatible  with  exactness. 

A compound  strip  of  metal,  as  represented  in  Fig.  16, 
is  free  from  many  of  these  difficulties,  and  if  of  sufficient 
length,  it  will  indicate  temperatures  with  great  delicacy.  A 
modification  of  this  instrument  is  known  under  the  name  of 
Breguet’s  thermometer.  It  consists 
of  a very  slender  strip  of  platinum, 
soldered  to  a similar  piece  of  silver, 
and  curved  into  a helix,  or  spiral,  a h. 
Fig.  17.  It  is  fastened  at  its  upper 
extremity  to  a metallic  support,  c c, 
c and  from  its  lower  portion  an  index 
projects,  which  plays  over  a graduated 
circle.  The  expansion  of  silver  is  more 
than  twice  as  great  as  that  of  platina ; 
when,  therefore,  the  temperature  of 
the  thin  spiral  rises,  curvature,  with  a corresponding  motion 
of  the  index,  takes-place  ; and  if  the  temperature  falls,  there 
is  a movement  in  the  opposite  direction,  as  has  been  already 
explained.  This  Breguet’s  thermometer  is  one  of  the  most 
delicate  instruments  we  have,  for  the  mass  of  the  spiral  is 
so  small  compared  with  the  mass  of  mercury  in  an  ordinary 
thermometer,  that  every  change  in  the  surrounding  temper- 
ature is  followed  with  rapidity  and  precision. 

For  many  purposes  in  science  and  the  arts,  it  is  necessary 
to  determine  temperatures  above  a red  heat.  Danieli’s  py- 
rometer is  intended  to  meet  these  occasions.  It  consists  of 
an  arrangement  by  which  the  expansion  of  a bar  of  iron  or 
platinum,  while  exposed  to  the  heat  to  be  measured,  is  reg- 
istered. The  amount  so  registered  is  subsequently  determ- 
ined upon  a divided  scale,  and  the  temperature  estimated 
therefrom.  By  the  aid  of  such  an  instrument  very  high  tem- 
peratures may  be  determined,  and  thus  it  has  been  shown 
that  brass  melts  at  1869^  Fahrenheit,  copper  at  1996^, 
gold  at  2200°,  and  cast  iron  at  2786°. 

The  thermometer  is  commonly  regarded  as  a measurer  of 
heat.  A little  consideration  will  satisfy  us  that  it  is  only 
so  in  a limited  sense  ; it  does  not  indicate  1he  quantity  of 

Describe  Bfeguet’s  thermometer.  AThy  is  this  instrument  so  sensitive? 
Describe  the  principle  of  Daniell’s  pyrometer.  Give  the  melting  points  of 
some  of  the  most  important  metals.  Does  the  thermometer  measure  the 
heat  to  which  it  is  exposed  ? 


CAPACITY  OF  BODIES  FOR  HEAT.  29 

heat  present  in  the  bodies  to  which  it  is  exposed,  for  if  im- 
mersed in  a glass  of  water  and  a bucket  of  water  drawn 
from  the  same  well,  it  stands  at  the  same  point ; but  of 
course  there  are  very  different  quantities  of  caloric  in  the  two 
cases.  It  is  not,  therefore,  the  quantity  of  heat,  but  the  in- 
tensity, which  it  measures ; that  is  to  say,  not  the  quantity 
abstractly,  but  the  quantity  contained  in  a given  space  ; and 
in  the  mercury  thermometer,  that  space  is  measured  by  the 
volume  of  the  mercury  in  the  instrument  itself.  It  does  not 
tell  how  much  heat  is  absolutely  present  in  the  substances 
to  which  it  is  exposed ; and  though  it  may  stand  at  the 
same  height  in  the  same  quantity  of  two  different  liquids,  it 
does  not  follow  that  those  liquids  contain  the  same  amount 
of  caloric,  as  we  are  immediately  to  see. 


LECTURE  VII. 

Capacity  of  Bodies  fop..  Heat. — Methods  of  determining 
Capacities.  — Warming. — Melting. — Cooling. — Mix 
ture. — Comparison  betiveen  the  Thermometer  and  Cal- 
orimeter.— Definition  of  Specific  Heat. 

Many  years  ago  it  was  discovered  by  Boyle,  that  if  two 
bottles  of  the  same  size  and  form  were  filled  with  different 
liquids,  and  placed  before  the  fire  so  as  to  receive  its  heat 
equally,  their  temperature  did  not  rise  similarly  ; thus,  if 
one  bottle  was  filled  with  water  and  the  other  with  quick- 
silver, the  temperature  of  the  latter  would  rise  much  more 
rapidly  than  that  of  the  former  ; and,  on  making  the  exper- 
iment with  a little  care,  it  will  be  found  that  the  same  quan- 
tity of  heat  will  raise  the  temperature  of  mercury  twice  as 
high  as  that  of  an  equal  volume  of  water. 

By  extending  these  experiments  to  other  substances,  it  has 
been  fully  proved  that  different  bodies  require  different 
amounts  of  heat  to  warm  them  equally. 


What  is  it  then,  that  it  does  actually  measure  ? What  is  meant  by  the 
intensity  of  heat?  Describe  Boyle’s  experiment  with  water  and  quicksilver. 
To  whtLt  general  result  do  such  experiments  lead  ? State  the  different  meth- 
ods by  which  capacities  for  heat  may  be  determined. 


30 


THE  CALORIMETER. 


Calorimetry. 

There  are  several  different  methods  by  which  the  capac- 
ity of  bodies  for  heat  may  be  determined,  such  as,  1st,  by 
warming  ; 2d,  by  melting  ; 3d,  by  cooling  ; 4th,  by  mixture. 

The  first  of  these  methods  has  already  been  illustrated  by 
the  experiment  of  Boyle.  It  consists  essentially  in  exposing 
the  same  weight  of  the  substances  to  be  tried  to  a uniform 
source  of  heat,  as,  for  example,  a bath  of  hot  water,  and  ex- 
amining how  high  their  temperature  has  risen  in  a given 
space  of  time.  Thus  it  will  be  found  that  it  takes  thirty 
times  as  long  to  warm  water  as  to  warm  mercury,  when 
equal  weights  are  used,  and  hence  we  infer  that  the  capac- 
ity of  water  for  heat  is  thirty  times  that  of  quicksilver. 

The  second  process  is  involved  in  the  action  of  the  calo- 
rimeter, the  operation  of  which  may  be  easily  understood 
from  Fig.  18.  Take  a solid  block  of 
ice,  a a,  in.  which  a cavity  of  the  form 
represented  at  b has  been  made,  and 
provide  a slab  of  ice,  c c,  which  may 
close  completely  the  mouth  of  the  cav- 
ity. Suppose  it  were  required  to  de- 
termine the  relative  capacities  of  water 
and  quicksilver  for  heat.  In  a glass 
flask,  d,  place  one  ounce  of  water,  and 
by  immersing  the  flask  in  a bath  of  hot  water,  raise  its  tem- 
perature up  to  a given  point,  as,  for  example,  200^ ; then 
place  the  flask  at  this  temperature  in  the  cavity  5,  and  put 
on  the  cover,  c c.  The  hot  water  in  the  flask  begins  to  cool, 
and  in  descending  to  32®,  the  point  to  which  it  will  event- 
ually come,  a certain  portion  of  the  surrounding  ice  is  melt- 
ed, the  water  resulting  therefrom  collects  in  the  bottom  of 
the  cavity,  and  when  the  cooling  is  complete,  it  may  be  pour- 
ed out  and  measured. 

In  the  next  place,  put  in  the  flask  one  ounce  of  quicksil- 
ver, the  temperature  of  which  is  raised  as  before  to  200® 
by  immersion  in  the  hot-water  bath ; deposit  the  flask  in 
the  ice  cavity,  and  put  on  the  cover.  As  the  quicksilver 
cools,  the  ice  melts,  and  when  the  collected  water  is  meas- 
ured, it  is  found  to  be  less  than  in  the  other  ca§e,  hi  the 

Give  an  illustration  of  the  first  process.  Show  how  the  capacities  of 
water  and  mercury  may  be  ascertained  by  the  second.  What  are  the  rela- 
tive capacities  of  equal  weights  of  these  bodies  ? 


METHODS  OP  DETERMINING  CAPACITIES. 


31 


proportion  of  1 to  30.  A given  weight  of  water  will  there- 
fore melt  30  times  as  much  ice  as  an  equal  weight  of  quick- 
silver, in  cooling  through  the  same  number  of  degrees. 

* The  calorimeter  of  Lavoisier,  which  is  represented  in 
Fig,  19,  acts  on  the  same  prin- 
ciple as  the  block  of  ice.  It  con- 
sists of  a set  of  tin  vessels  within 
each  other  ; in  the  central  one, 

<1,  the  substance  to  be  examined 
is  placed,  and  between  this  and 
the  next  vessel,  at  b,  the  ice  to 
be  melted  is  introduced,  broken 
into  small  fragments ; the  water 
arising  from  the  melting  flowing 
off  through  a stop-cock,  c,  at  the 
bottom  into  a measuring  glass ; 
and  in  order  to  avoid  any  por- 
tion of  the  ice  being  melted  by  the  warm  external  air,  an- 
other layer  of  fragments  of  ice  is  placed  on  the  outside  at  d, 
and  the  water  arising  from  it  is  carried  off  by  a lateral  stop- 
cock, e. 

The  third  process,  the  method  by  cooling,  known  also  as 
the  method  of  Dulong  and  Petit,  consists  essentially  in  as- 
certaining the  length  of  time  required  to  cool  through  a given 
number  of  degrees.  A substance  which,  like  water,  has  a 
great  capacity  for  caloric,  and  therefore  contains  a large 
amount  of  it,  requires  a greater  length  of  time  to  cool ; but 
one  like  quicksilver,  the  capacity  of  which  is  small,  having 
less  heat  to  give  forth,  requires  a corresponding  short  space 
of  time.  The  method  by  cooling  requires  -several  precau- 
tions ; among  others,  the  bodies  under  investigation  should 
be  placed  in  vacuo.  It  gives  very  exact  results. 

The  method  by  mixture  may  be  readily  understood.  If 
a pint  of  water  at  50°  be  mixed  with  a pint  of  water  at 
100^,  the  temperature  will  be  75^,  that  is  the  mean.  But 
if  a pinL  of  mercury  at  100^  be  mixed  with  a pint  of  water 
at  40°,  the  temperature  of  the  mixture  will  be  60°  : so  that 
the  forty  degrees  lost  by  the  mercury  can  only  raise  the  tem- 
perature of  the  water  twenty  degrees.  It  appears,  there- 
fore, that  when  equal  volumes  of  these  fluids  are  examined, 
the  capacity  of  the  water  for  heat  is  about  twice  as  great 

Describe  the  calorimeter  of  Lavoisier,  Describe  the  method  of  Dulong 
and  Petit  Describe  the  method  by  mixture. 


Fig.  19, 


32 


METHODS  OF  DETERMINING  CAPACITIES. 


as  that  of  mercury,  and  of  course  the  result  becomes  still 
more  striking  when  equal  weights  are  used,  being  then,  as 
we  have  seen,  in  the  proportion  of  1 to  30. 

The  method  of  mixtures  is  not  limited  to  the  investiga- 
tion of  liquid  substances,  but  it  may  also  be  extended  to  sol- 
ids. Thus,  if  a pound  of  copper,  heated  to  300°,  be  plunged 
into  a pound  of  water  at  50°,  the  resulting  temperature  is 
72°  ; from  which  it  appears  that  the  capacity  of  water  for 
heat  is  about  ten  times  as  great  as  that  of  copper. 

By  resorting  to  these  various  methods,  the  capacities  of  a 
great  number  of  substances  have  been  determined,  and  in 
the  treatises  on  chemistry,  tables  exhibiting  such  results  are 
given.  But  it  will  have  been  noticed,  from  the  foregoing 
instances,  that  it  is  not  the  absolute  quantities  of  heat  in 
bodies  that  we  thus  determine,  but  only  relative  quantities 
in  substances  compared  together.  Such  tables  require, 
therefore,  one  substance  to  be  selected  with  which  all  the 
others  may  be  compared,  and  for  solids  and  liquids  water 
has  been  chosen.  Its  capacity  for  heat  is  represented  by 
1*000,  and  with  it  they  are  compared.  For  gaseous  bodies 
atmospheric  air  is  chosen. 


Capacity  of  Bodies  for  Heat. 


Water .... 

. 1000 

Cobalt  . . . 

. . 106-96 

Ice 

. 513 

Zinc  .... 

. . 95-55 

Charcoal  . . . 

. 414 

Copper  . . . 

. . 95-15 

Sulphur  . . . 

. 241 

Arsenic . . . 

. . 81-40 

Glass  .... 

. 203 

Silver  . . . 

. . 57-01 

Diamond  . . . 

. 147 

Gold.  . . . 

. . 32-44 

Iron  .... 

. 113-79 

Platinum  . . 

. . 32-43 

Nickel .... 

. 108-63 

Mercury  . . 

. . 33-32 

From  this  it  appears  that  the  capacity  of  ice  for  heat  is 
nearly  half  that  of  water,  which  stands  at  the  head  of  all 
solid  and  liquid  substances.  ..  In  the  form  of  steam  the  ca- 
pacity of  water  is  less  than  in  the  liquid  form,  in  the  ratio 
of  847  to  1000  for  equal  weights.  The  calorific  capacity  of 
a substance  therefore  changes  with  its  physical  condition. 

The  method  which  has  been  resorted  to  for  determining 
the  capacity  of  gases,  is  to  pass  them,  when  heated  carefully 
to  212°,  through  a spiral  tube  immersed  in  water,  the  tem- 
perature of  which  is  measured.  Owing  to  experimental  dif- 

Is  this  limited  to  liquid  substances  ? Do  we  thus  determine  the  absolute 
quantities  of  heat  in  bodies  ? What  substance  is  used  to  compare  solids 
and  liquids  ? What  is  the  substance  for  gases  ? 


black’s  doctrine  op  capacities. 


33 


ficulties,  the'  results  arrived  at  by  different  chemists  exhibit 
considerable  variation. 

By  contrasting  the  nature  of  the  results  given  by  the  cal- 
orimeter, Eig.  19,  with  the  indications  of  a thermometer, 
we  shall  see  more  clearly  what  it  is  that  the  latter  instru- 
ment in  reality  points  out.  The  calorimeter  measures  quan- 
tities of  heat,  the  thermometer  intensities.  As  has  been 
said,  a thermometer  placed  in  two  vessels  of  different  ca- 
pacities, filled  with  water  from  the  same  source,  will  stand 
at  the  same  height  in  both,  and  indicate  the  same  temper- 
ature. But  it  needs  no  experiment  to  assure  us  that,  if  these 
different  quantities  of  water  were  placed  successively  in  the 
interior  of  the  calorimeter,  they  would  melt  different  quan- 
tities of  ice,  the  one  melting  more  of  the  ice  in  proportion  to 
its  greater  weight  compared  with  the  other. 

Dr.  Black,  who  was  one  of  the  early  investigators  of  these 
phenomena,  introduced  the  term  “ Capacity  of  Bodies  for 
Heat,”  implying  the  idea  that  this  principle,  entering  their 
pores,  could  be  taken  up  by  different  bodies  in  different 
amounts.  Thus,  if  we  have  two  pieces  of  sponge  of  the 
same  size,  one  of  which  is  of  a very  dense,  and  the  other  of 
a porous  texture,  and  cause  them  to  imbibe  as  much  water 
as  they  can  hold,  the  porous  sponge  will  of  course  contain 
the  greater  quantity.  These  sponges  may  therefore  be  said 
to  have  different  “ capacities  for  water and  this  is  precisely 
the  idea  which  is  conveyed  in  Black’s  doctrine  of  capacity. 

But,  upon  these  principles,  it  would  follow  that  the  lighter 
a body  is,  that  is,  the  greater  the  interstices  between  its  atoms, 
the  more  caloric  it  should  be  able  to  contain.  Oil,  there- 
fore, which  will  float  upon  water,  ought  to  have  a greater 
capacity  for  heat  than  water ; but,  in  fact,  it  is  the  reverse, 
for  its  capacity,  instead  of  being  greater,  is  not  one  half.  To 
avoid  these  difficulties,  the  term  specific  heat  has  been  in- 
troduced by  most  writers,  and  the  term  capacity  abandoned, 
a change  which  I think  is  to  be  regretted,  especially  when 
it  is  recollected  that  this  objection  does  not  contemplate  the 
difference  of  the  weight  of  atoms. 

The  specific  heat  of  bodies,  or  their  capacity  for  caloric, 
increases  with  their  temperature.  Upon  Black’s  doctrine, 


How  do  the  indications  of  the  calorimeter  compare  with  those  of  the  ther- 
mometer ? On  what  analogy  is  Black’s  doctrine  of  “ capacity”  founded  ? 
What  is  the  objection  to  this  doctrine?  What  is  meant  by  specific  heat? 
Does  the  capacity  of  bodies  change  with  their  temperature  ? 


34 


VARIATIONS  OP  SPECIFIC  HEAT. 


the  cause  of  this  is  readily  understood,  for,  in  simple  lan- 
guage, the  pores  become  larger,  and  there  is  therefore  room 
for  more  heat.  Solid  substances,  when  violently  compressed, 
evolve  a portion  of  their  caloric  : thus,  a piece.,  of  soft  iron, 
when  hammered,  becomes  red  hot.  The  doctrine  of  Black 
here  again  ofters  a ready  explanation,  for  on  the  same  prin- 
ciple that  a sponge,  when  compressed,  allows  a certain  por- 
tion-of  its  water  to  exude,  so  the  metalline  mass,  when  its 
particles  are  forced  together,  allows  some  of  its  caloric  to 
escape. 


LECTURE  VIIL 

Capacity  for  Heat  and  Latent  Heat. — Variahility  of 
Capacities  under  Compression  and  Dilatation. — The- 
ory  of  the  Formation  of  Clouds. — The  Fire  Syringe. — 
Cold  in  the  upper  Regions  of  the  Air.  — Connection 
between  Specific  Heats  and  Atomic.  Weights. — Latent 
Heat. — Caloric  of  Fluidity. 

When  the  volume  of  a gas  increases,  its  capacity  for  heat 
increases,  and  a diminution  of  volume  is  attended  with  a 
diminution  of  capacity.  Thus,  if  we  place  a 
Breguet’s  thermometer  under  the  receiver  of  an 
air  pump,  and  exhaust  rapidly,  a sudden  reduc- 
tion of  temperature  is  indicated,  arising  from  the 
fact  that,  as  the  rarefaction  is  effected,  the  ca- 
pacity increases,  an  increase  which  is  satisfied  at 
the  expense  of  a portion  of  the  sensible  heat. 
Upon  the  same  principle  we  can  explain  the  sudden  ap- 
pearance of  a fog  or  cloud,  when  moist  air  is  quickly  rare- 
fied. It  will  be  seen,  when  we  speak  of  the  nature  of  va- 
pors, that  the  quantity  of  vapor  which  can  exist  in  a given 
space  depends  on  the  temperature  ; thus,  if  a space  sat- 
urated with  vapor  is  cooled,  a portion  of  the  vapor  assumes 
the  liquid  form.  When,  therefore,  by  the  aid  of  an  air- 
pump,  we  suddenly  rarefy  air  saturated  with  moisture  under 


Does  the  capacity  of  bodies  change  under  compression?  How  is  this  ex- 
plained agreeably  to  Black’s  doctrine  ? When  the  volume  of  a gas  changes, 
what  are  the  changes  in  its  specific  heat  ? What  is  the  fact  which  the  exper- 
iment of  Fig.  20  proves  ? What  is  the  theory  of  the  production  of  clouds  ? 


Fig.  20. 


FORMATION  OF  A CLOUD. 


3f 


a receiver,  the  capacity  increases,  cold  is  produced,  and  a 
part  of  the  water  takes  on  the  form  of  drops.  It  Fig.  21. 
is  on  this  principle  that  the  nephelescope  acts  : it 
consists  of  a receiver,  a,  Fig.  21,  connected  with 
a flask,  Cy  by  an  intervening  stop-cock,  b;  the 
stop-cock  being  closed,  the  receiver  is  exhausted 
by  the  pump,  and  now,  on  suddenly  opening  the 
stop-cock,  so  that  the  air  contained  in  the  flask 
may  rapidly  expand  into  the  receiver,  a mist  or 
cloud  makes  its  appearance,  due  to  the  deposit  of 
water  in  the  form  of  minute  drops.  If  the  air  at 
the  time  be  very  dry,  it  may  be  purposely  ren- 
dered moist  by  being  exposed  to  water. 

When  atmospheric  air  is  suddenly  compressed,  its  capac- 
ity for  heat  diminishes ; this  is  well  shown  by  an  in-  Fi^.22. 
strument  such  as  is  represented  in  Fig.  22,  consisting  ^ 
of  a syringe,  with  a piston  moving  perfectly  air  tight 
in  it.  On  the  end  of  the  piston  there  is  an  excavation, 
in  which  a piece  of  tinder  may  be  fastened ; the  pis- 
ton being  rapidly  forced  into  the  syringe,  the  air  is 
compressed,  the  capacity  for  heat  becomes  less,  caloric 
is  evolved,  and  the  tinder  set  on  fire.  At  one  time 
these  syringes  were  used  as  a means  of  obtaining  fire. 

The  variation  in  capacity  of  substances  under  variation 
of  volume  may  be  clearly  understood  and  readily  borne  in 
mind  by  Black’s  doctrine,  as  illustrated  in  the  case  of  a 
moistened  sponge.  If  a sponge  which  has  imbibed  as  much 
water  as  it  can  hold  be  compressed,  a portion  of  the  water 
exudes,  just  as  the  air  in  the  syringe  allows  a portion  of  iU 
heat  to  escape  when  pressure  is  made.  On  relaxing  the 
force  on  the  sponge,  and  allowing  it  to  dilate,  it  will  take 
up  an  increased  quantity  of  water  ; and  air,  when  suddenly 
dilated,  as  we  have  seen,  has  its  capacity  for  heat  increased. 

From  these  facts,  it  appears  that  the  heat  of  bodies  exists 
under  two  different  forms,  as  sensible  and  insensible  heat. 
In  the  experiment  with  the  syringe,  just  related,  the  heat 
that  sets  fire  to  the  tinder  existed  previously  to  compression 
in  the  air  ; it  existed  as  insensible  heat,  but  during  the  com- 
pression it  put  on  the  form  of  sensible  heat.  The  same  tran- 


Describe  the  nephelescope.  What  is  the  result  of  the  action  of  this  in- 
strument? When  air  is  compressed,  why  does  it  emit  heat?  How  can 
these  changes  be  accounted  for  by  Black’s  doctrine  ? What  are  the  rela- 
tions betw’een  sensible  and  insensible  heat  ? 


36 


SENSIBLE  AND  INSENSIBLE  HEAT. 


sition  is  also  recognised  in  the  action  of  the  nephelescope ; 
the  heat,  which  was  sensible  before  rarefaction,  becomes  in- 
sensible, and  cold,  or  a depression  of  temperature  is  the  result. 

The  great  degree  of  cold  which  reigns  in  the  upper  re- 
gions of  the  atmosphere  is  due,  to  a considerable  extent,  to 
the  capacity  of  that  dilated  air  for  heat.  On  the  same  prin- 
ciple we  can  explain  the  formation  of  clouds  from  transpar- 
ent atmospheric  air  : a stratum  of  air,  reposing  on  the  sur- 
face of  the  sea,  or  the  moist  earth,  becomes  saturated  with 
vapor ; by  the  warmth  of  the  sun  or  other  causes,  it  begins 
to  rise  in  the  atmosphere,  and  as  it  rises  it  expands,  because 
the  pressure  upon  it  is  continually  becoming  less.  An  in- 
creased capacity  is  the  result  of  its  dilatation,  and,  as  is  the 
case  in  the  nephelescope,  cold  is  produced,  and  a deposit  of 
a part  of  the  moisture  takes  place  ; this  moisture,  appearing 
under  the  form  of  minute  drops,  is  what  we  call  a cloud. 

From  the  small  capacity  of  quicksilver  for  heat,'  we  see 
one  of  the  reasons  that  it  is  a suitable  substance  for  forming 
thermometers ; it  warms  rapidly  and  cools  rapidly,  and  there- 
fore follows  variations  of  temperature  much  more  promptly 
than  water  and  most  other  liquids. 

There  is  a connection  between  the  specific  heat  of  sev- 
eral simple  bodies  and  their  atomic  weights,  pointing  out 
the  fact  that  elementary  atoms  have  in  many  instances  the 
same  specific  heat ; recently  the  same  conclusion  has  been 
established  in  the  case  of  certain  oxides,  carbonates,  and 
sulphates.  • 


Table  of  the  Sjpecific  Heats  of  Elementary  Atoms. 


Iron  .... 

. . 3-0928 

Sulphur  . . . 

. 3*2657 

Zinc .... 

. . 3-0872 

Mercury  . . . 

. 3*7128 

Copper  . . . 

. . 3 0172 

Silver  .... 

. 6*1742 

Lead .... 

. . 3-2581 

Arsenic .... 

. 6-1326 

Tin  ...  . 

. . 3-3121 

Antimony  . . . 

. 6-5615 

Nickel  . . . 

. . 3-2176 

Gold 

. 6-4623 

Cobalt  . . . 

. . 3-1628  ’ 

Iodine  .... 

. 6-8462 

Platinum  . . 

. . 3-2054 

Bismuth  . . . 

. 2-1917 

From  this  table  it  appears  that  the  first  ten  substances 
show  a close  approximation  in  their  capacities  for  heat,  if 
the  quantities  used  be  in  proportion  to  the  atomic  weights, 
instead  of  equal  weights  ; that  the  next  five  have  a double 
capacity ; and  the  last  a capacity  less  by  about  one  third. 

Describe  the  mode  in  which  clouds  form.  Why  does  the  capacity  of 
quicksilver  fit  it  for  a thermometric  liquid  ? What  is  h-*  relation  of  the 
specific  heat  of  many  elementary  bodies  ? 


LATENT  HEAT. 


37 


Latent  Heat. 

First  Change  of  Form.  Heat  of  Fluidity. 

When  solid  substances,  which  can  resist  a due  tempera- 
ture without  decomposition,  are  exposed  to  an  increasing 
heat,  a point  is  eventually  reached  at  which  they  assume 
the  liquid  state.  This  point,  known  as  the  point  of  fusion 
or  melting  point,  may  be  regarded  as  fixed  for  each  sub- 
stance. For  mercury  it  is  39*^  below  the  zero  of  the  ther- 
mometer ; for  iron,  about  2800^  above. 


Table  of  the  Melting  Points  of  Bodies. 


Iron 

. . 2800 

Sulphur  .... 

. 232 

Gold  . . . . 

. . 2016 

Wax  . . . . ; 

. 142 

Silver  . . . . 

. . 1873 

Phosphorus  . . . 

. 108 

Zinc  . . . . 

. . 773 

Tallow  .... 

. 92 

Lead  . . . . 

. . 612 

Olive  Oil  .... 

. 36 

Tin 

. . 442 

Ice 

. 32 

Potassium  . . 

. . 135 

Mercury  .... 

. —39 

Some  substances,  perhaps  all  to  a greater  or  less  extent, 
pass  through  a condition  intervening  between  the  solid  and 
liquid  state,  assuming  a pasty  consistency.  The  manufac- 
ture of  glass  depends  on  such  a property ; it^is  also  striking- 
ly shown  by  various  oils  and  wax.  Indeed,  different  liquids 
may  be  said  to  present  different  degrees  of  liquidity  : this  is 
well  seen  when  sulphuric  acid,  a dense,  sluggishly-moving 
body,  is  compared  with  sulphuric  ether,  a substance  of  re- 
markable mobility.  The  liquidity  of  the  liquid  state  seems 
generally  to  be  increased  by  elevation  of  temperature. 

If  we  take  a mass  of  ice,  the  temperature  of  which  is  at 
the  zero  point,  and  bring  it  into  a warm  room,  examining 
the  circumstances  under  which  its  temperature  rises,  they 
will  be  found  as  follows  : the  mass  of  ice,  like  any  other 
solid  body,  warms  with  regularity  until  it  reaches  32?  ; then, 
for  a considerable  period  of  time,  no  farther  elevation  is  per- 
ceptible, but  it  undergoes  a molecular  change,  assuming  the 
liquid  condition ; when  this  is  complete,  the  temperature 
again  commences  to  rise. 

That  we  may  have  precise  views  of  these  facts,  let  us  sup- 
pose that  the  mass  of  ice  and  the  warm  room  into  which  it 
is  carried  have  such  relations  to  each  other  that  the  temper- 
ature of  the  former  can  rise  from  the  zero  point  one  degree 
per  minute  ; for  thirty-two  minutes  the  temperature  of  the 
Describe  the  change  which  ice  undergoes  when  warming. 


CALORIC  OF  FLUIDITY. 


38 

ice  will  be  found  to  increase,  and  at  the  end  of  that  time,  a 
thermometer,  if  applied,  would  stand  at  32°.  But  now,  al- 
though  the  heat  is  still  entering  the  ice  at  the  rate  of  a de- 
gree per  minute,  the  process  of  warming  ceases,  and  for  140 
minutes  no  farther  rise  takes  place  ; the  ice  now  commences 
to  melt,  and  in  140  minutes  the  liquefaction  is  complete. 
The  temperature  then  again  rises,  and  continues  to  do  so 

with  regularity.  . . . n 

We  infer  from  results  like  the  foregoing,  that  about  14U 
degrees  of  heat  are  absorbed  by  ice  in  passing  into  the  con- 
dition  of  water  ; and  as  this  heat  is  not  discoverable  by  the 
thermometer,  it  is  designated  as  latent  heat. 

A similar  fact  appears  when  any  liquid,  such  as  water, 
passes  into  the  gaseous  or  vaporous  condition.  Thus,  if  some 
water  be  exposed  to  a fire  which  can  raise  its  temperature 
at  the  rate  of  one  degree  per  minute,  that  effect  will  con- 
tinue until  212°  are  reached  ; at  that  point,  no  matter  how 
much  the  heat  be  increased,  the  temperature  remains  sta^ 
tionary.  The  water  undergoes  a change  of  form,  assuming 
the  condition  of  a vapor,  and  the  change  is  completed  in  about 
1000  minutes.  In  this,  as  in  the  former  instance,  we  infer 
that  a large  amount  of  heat  has  become  latent,  or  undis- 
coverable  by  the  thermometer,  and  that  it  is  occupied  m es- 
tablishing the  elastie  form  which  the  water  has  assumed. 

The  caloric  which  thus  disappears  when  a solid  assumes 
the  liquid  form,  takes  also  the  designation  of  caloric  of  fluid- 
ity, and  that  which  disappears  in  the  formation  of  a vapor, 
the  caloric  of  elasticity. 


Table  of  the  Caloric  of  Fluidity  of  Bodies. 


Water . . . . 

, . . 142° 

Zinc  . . . 

. . . 4930 

Sulphur  . . . 

, . . 145'^ 

Tin.  . . . 

. . . 500° 

Lead  . . . . 

, . . 162'^ 

Bismuth  . . 

. . . 550° 

Beeswax  . . . 

. . . 175"^ 

By  the  method  of  mixtures  the  same  results  may  be  es- 
tablished ; thus,  if  a pound  of  water  at  32°  is  mixed  with 
a pound  at  172°,  the  mixture  will  have  the  mean  temper- 
ature, that  is,  102°  ; but  if  a pound  of  ice  at  32°  be  mixed 

Is  there  any  pause  in  the  elevation  of  its  temperature?  How  many  de- 
crees of  heat  are  absorbed  during  the  liquefaction  of  ice  ? What  is  latent 
heat  ? How  many  degrees  of  heat  are  absorbed  during  the  vaporization  of 
water?  What  is  the  latent  heat  of  steam?  What  is  caloric  of  fluidity? 
What  is  caloric  of  elasticity  ? How  can  the  doctrine  of  latent  heat  be  e» 
tablished  by  the  method  of  mixtures  ? 


HEAT  EVOLVED  IN  SOLIDIFICATION. 


39 


with  a pound  of  water  at  172°,  the  mixture  still  remains  at 
32°,  and  the  reason  is  clear,  from  the  foregoing  considera- 
tions, that  ice,  in  passing  into  the  liquid  state,  requires  140° 
of  caloric  of  fluidity  which  are  rendered  latent. 


LECTURE  IX. 

Latent  Heat. — Heat  evolved  in  Solidification. — Theory 
of  freezing  Mixtures. — Expansion  during  Solidifica- 
tion.— Fixity  of  the  Melting  Point. — Latent  Heat  con- 
nected with  the  Duration  of  the  Seasons. — Nature  of 
Vapors. — Caloric  of  Elasticity. 

When  a liquid  assumes  the  solid  form,  a considerable 
amount  of  heat  is  evolved.  The  cause  is  readily  understood, 
from  what  we  have  seen  taking  place  during  the  reverse 
process  ; which  has  led  us  to  the  fact  that  the  difference  be- 
tween any  given  solid  and  the  liquid  which  arises  from  it 
by  melting  is  in  the  large  amount  of  latent  heat  which  is 
found  in  the  latter,  and  which  is  occupied  in  giving  it  its 
form. 

A saturated  solution  of  sulphate  of  soda  may  be  cooled 
from  its  boiling  point  to  common  temperatures,  in  a vessel 
tightly  corked,  without  solidification  taking 
place  ; but  when  the  cork  is  withdrawn  crys- 
tallization ensues,  and  heat  is  evolved.  This 
may  be  proved  by  taking  a bottle,  a a,  Fig.  23, 
filled  with  such  a solution  ; and  having  intro- 
duced the  bulb  of  an  air  thermometer  through 
the  neck,  h,  by  means  of  an  air-tight  cork,  the 
mouth,  c,  of  the  bottle  is  to  be  carefully  stopped. 

When  the  whole  apparatus  has  reached  the  or- 
dinaiy  temperature  of  the  air,  the  stopper  at  c 
is  withdrawn,  and  solidification  at  once  takes  place,  or,  if 
it  should  at  first  fail,  the  introduction  of  a crystal  of  sul- 
phate of  soda  will  bring  it  on.  At  that  moment  it  will  be 
perceived  that  not  only  does  the  thermometer  indicate  a 
rise  of  temperature,  but  if  the  bottle  be  grasped,  it  will  be 
found  to  be  sensibly  warm. 

Is  heat  absorbed  or  evolved  when  a liquid  solidifies  ? What  is  the  cause 
of  this  ? How  can  it  be  illustrated  with  a solution  of  sulphate  of  soda  ? 


Fig.  23. 


40 


FREEZING  MIXTURE. 


With  care,  water  may  he  cooled  to  a point  far  below  that 
of  freezing  without  assuming  the  solid  form.  If,  under  these 
unusual  circumstances,  it  be  agitated,  solidification  of  a part 
of  the  water  ensues,  and  heat  is  evolved,  the  temperature 
rising  to  32°. 

On  these  principles  depends  the  action  of  freezing  mix- 
tures, of  which  the  following  is  an  example  : If  we  take 
eight  parts  of  crystallized  sulphate  of  soda,  and  mix  it  in  a 
thin  tumbler  with  five  parts  of  hydrochloric  acid,  the  sul- 
phate of  soda,  from  being  a solid,  assumes  the  liquid  form ; 
and  taking,  in  order  to  effect  that  change,  of  form,  caloric 
from  surrounding  bodies,  it  reduces  their  temperature.  This 
may  be  shown  by  placing  four  parts  of  water  in  a thin  glass 
test  tube,  and  stirring  it  about  in  the  mixture  ; the  water 
speedily  freezes,  even  though  the  experiment  may  be  made 
on  a warm  summer  day. 


Table  of  Freezing  Mixtures. 


Mixtures. 

Pts. 

Tliennometer  Sinks. 

Deg.  of  Cold. 

Nitrate  of  Ammonia  . 
Water 

1 

1 

from -{-50°  to-|-4° 

46° 

Sulphate  of  Soda  . . 

Hydrochloric  Acid 

8 

5 

from 50°  to  0 

50° 

Snow  or  pounded  Ice 
Common  Salt  . . . 

2 

1 

to  5° 

* 

Snow  ...... 

Diluted  Nitric  Acid  . 

3 

2 

from  0°  to  —46° 

46° 

All  these  mixtures  depend  essentially  on  the  principle  un- 
der consideration — that  latent  heat  must  be  furnished  to  a 
substance  passing  from  the  solid  to  the  liquid  state.  They 
consist  of  various  solid  substances,  the  liquefaction  of  which 
is  brought  about  by  the  action  of  other  bodies  : thus,  in  the 
instance  we  have  seen,  the  sulphate  of  soda  is  brought  from 
the  solid  to  the  liquid  state  by  hydrochloric  acid,  in  which 
it  dissolves,  and  heat  is  necessarily  absorbed. 

Many  substances,  when  solidifying,  expand.  This  is  the 
case  with  water,  in  which  the  amount  of  expansion  is  about 
|-th  of  the  bulk.  The  force  which  is  exerted  under  these 
circumstances  is  very  great,  and  capable  of  tearing  open  the 
strpngest  vessels.  On  a small  scale,  this  may  be  easily 

Can  water  be  cooled  below  32°  without  freezing  ? Give  an  example  of 
a freezing  mixture.  What  are  the  principles  on  which  freezing  mixtures 
act  ? What  is  the  amount  of  the  expansion  of  water  in  the  act  of  freezing  ? 


SOLIDIFICATION  OF  WATER. 


41 


shown  by  filling  a bottle  full  of  water,  and,  having  intro- 
duced the  cork,  fastening  it  tightly  down  with  a piece  of 
wire.  On  putting  such  a bottle  into  a freezing  mixture,  for 
example,  snow  moistened  with  nitric  acid,  congelation 
promptly  takes  place,  and  the  bottle  is  burst. 

All  processes  of  freezing  are  therefore  processes  of  warm- 
ing, for  the  heat  which  has  given  the  liquid  form  reappears 
when  solidification  takes  place. 

The  freezing  point  of  water  is  usually  spoken  of  as  a fixed 
point,  and  is  marked  as  such  upon  the  scales  of  our  ther- 
mometers ; but  if  water  be  cooled  without  allowing  any 
movement  or  agitation  of  its  parts,  it  may  be  brought  as  low 
as  15°.  It  is  then  in  the  same  condition  as  the  saturated 
solution  of  sulphate  of  soda  just  alluded  to.  The  slightest 
motion  is  sufficient  to  solidify  it.  But,  though  water  will 
retain  its  liquid  form  far  below  its  freezing  point,  ice  can  not 
be  brought  above  32^  without  melting.  The  melting  of  ice, 
and  not  the  freezing  of  water,  is  therefore  the  fixed  ther- 
mometric point. 

We  have  seen  that  the  possession  of  a point  of  maximum 
density  by  water  exerts  a great  effect  upon  the  duration  of 
the  seasons ; a similar  observation  might  be  made  as  re- 
spects its  latent  heat.  If  ice,  by  the  absorption  of  a single 
degree  of  heat,  when  it  passes  from  32°,  could  turn  into 
water,  the  great  deposits  of  winter  would  suddenly  melt,  and 
inundations  be  frequent ; or,  if  water,  by  losing  a single  de- 
gree of  heat,  turned  into  ice,  freezing  would  go  on  with  great 
rapidity.  To  the  melting  of  ice,  or  the  freezing  of  water, 
time  is  necessary  ; the  140°  of  latent  heat  have  to  be  dis- 
posed of ; this,  therefore,  serves  to  procrastinate  the  approach 
of  winter,  and  causes  the  spring  to  come  forward  with  more 
measured  steps.  In  autumn  the  water  has  140°  degrees  of 
heat  to  give  out  to  surrounding  bodies  before  it  solidifies ; 
in  spring  it  must  receive  the  same  amount  before  it  will 
melt.  This,  therefore,  serves  as  a check  upon  sudden 
changes  in  the  seasons. 

Second  Change  of  Form — Heat  of  Elasticity. 

Having  thus  discussed  the  leading  facts  observed  in  the 

How  may  the  force  with  which  this  expansion  takes  place  be  illustrated? 
Is  the  freezing  point  of  water  a fixed  thermometric  point  ? How  low  can 
\vater  be  cooled  without  freezing  ? Is  the  melting  of  ice,  or  the  freezing  ot 
water,  the  fixed  thermometric  point  ? What  connection  has  the  latent  heat 
of  water  with  the  duration  of  the  seasons  ? 


42 


PROPERTIES  OP  VAPORS. 


change  from  the  solid  to  the  liquid  condition,  let  us  now 
turn  our  attention  to  the  second  change  of  form,  the  passage 
from  the  liquid  to  the  gaseous  state. 

Exposed  to  a rise  of  temperature,  liquid  substances  boil 
at  a particular  point,  which  varies  with  their  nature,  as  the 
following  table  shows. 


Table  of  Boiling  Points, 


Ether 

96^^ 

m. 

Nitric  Arid  . . • 

• 248° 

Sulphuret  of  Carbon 

118^ 

Oil  of  Turpentine 

. 314° 

Ammonia  .... 

140° 

Phosphorus  . . . 

. 554° 

Alcohol 

173° 

Sulphuric  Acid  . 

. 620° 

Water 

212° 

Mercury  . . . , 

. 662° 

A technical  distinction  is  made  between  a gas  and  a va- 
por ; by  the  latter  we  understand  a gas  which  will  readily 
take  on  the  liquid  form. 

Some  of  the  leading  peculiarities  in  the  constitution  of 
Fig.  24.  vapors  may  be  exhibited  by  the  following 
experiment : Take  a glass  tube,  a Fig- 
24,  with  a bulb,  b,  blown  on  its  upper  ex- 
tremity ; pour  water  into  the  bulb,  filling 
the  tube  to  within  an  inch  or  two  of  the 
end  ; this  vacant  ^space  fill  with  sulphuric 
ether  ; and  now,  closing  the  end  of  the  tube 
with  the  finger,  invert  it  in  a glass  of  water, 
as  is  represented  in  the  figure.  The  ether,  being  much  light- 
er than  water,  at  once  rises  to  the  upper  part  of  the  bulb, 
as  is  shown  by  the  light  space,  the  bulb  being  of  course  full 
of  ether  and  water  conjointly. 

On  the  application  of  a spirit  lamp  the  ether  vaporizes, 
and  presses  the  water  out  of  the  bulb  into  the  glass  cup. 
Three  important  facts  may  now  be  established. 

1st.  Vapors  occupy  more  space  than  the  liquids  from 
which  they  arise. 

2d.  They  have  not  a misty  or  fog-like  appearance,  but 
are  perfectly  transparent. 

3d.  When  their  temperature  is  reduced,  they  collapse  to 
the  liquid  state. 

That  the  first  of  these  observations  is  true,  is  at  once  seen 
on  comparing  the  quantity  of  ether  with  the  volume  of  va- 


What  is  the  distinction  between  a gas  and  a vapor?  Describe  the  exper- 
iment represented  in  Fig.  24.  VV^hat  is  the  difference  between  a vapor  and 
the  liquid  which  forms  it,  as  to  volume  ? Have  vapors  necessarily  a cloudy 
appearance  ? 


VAPORIZATION. 


43 


por  which  has  risen  from  it ; the  ether  occupying  but  a small 
space  at  the  top  of  the  bulb,  the  vapor  fills  it  entirely.  We 
perceive,  moreover,  that  ethereal  vapor  does  not  possess  that 
cloudy  appearance  which  is  popularly  attached  to  the  term 
vapor,  but  that  it  is  as  transparent  as  atmospheric  air.  And, 
on  removing  the  lamp,  so  that  the  temperature  may  fall,  the 
liquid  rushes  up  violently  into  the  bulb,  exhibiting  the  ready 
collapse  of  the  ether  vapor  into  the  condition  of  a liquid. 

We  have  already  proved  that  a large  amount  of  heat  be- 
comes latent,  constituting  the  caloric  of  elasticity  of  vapors. 
The  temperature  of  steam  is  212^,  as  is  that  of  the  water 
from  which  it  rises ; but  it  contains  about  1000°  of  latent 
heat,  which  gives  to  it  its  new  form.  Difierent  vapors  pos- 
sess different  quantities  of  latent  heat ; thus,  for  ether,  the 
number  is  163° ; for  alcohol,  376°  ; and,  as  we  have  said,  for 
water,  1000° ; or,  according  to  the  recent  exact  experiments 
of  Brix,  972°.  It  is  this  great  quantity  of  caloric  which 
constitutes  steam  so  efficient  an  agent  for  warming.  The 
steam  arising  from  one  gallon  of  water  will  raise  the  tem- 
perature of  five  gallons  and  a quarter  from  the  freezing  to 
the  boiling  point ; its  caloric  of  elasticity  is  nearly  sufficient, 
were  the  steam  a solid  body,  to  make  it  visibly  red  hot  in 
the  daylight.  In  the  warming  of  buildings  by  steam  pipes, 
each  square  foot  of  their  surface  will  heat  200  cubic  feet  of 
surrounding  air  to  75°,  and  will  require  about  170  cubic 
inches  of  boiler  capacity  for  its  proper  supply. 


LECTURE  X. 

Vaporization. — Vapors  form  at  all  Temperatures, — Form 
instantly  in  a Void. — Effects  of  removing  Pressure. — 
Measure  of  Elastic  Force  of  Vapors.  — Cumulative 
Pressure. — Failure  of  Marriotte's  Law. — Elasticity 
increases  with  Temperature. — Maximum  Density  of 
Vapors. 

Vaporization  goes  on  at  all  temperatures.  It  is  not  nec- 
essary that  the  boiling  point  should  be  reached ; even  ice 

On  reduction  of  the  temperature,  what  phenomena  do  they  exhibit? 
How  are  these  three  facts  proved  ? What  is  the  amount  of  caloric  of  elas- 
ticity of  steam  ? Mention  it  also  in  the  case  of  ether  and  alcohol. 


44 


EFFECTS  OF  CHANGE  OF  PRESSURE. 


-will  evaporate  away.  The  thin  films  of  this  substance  often 

F\g.  25.  ’ seen  incrusting  windows  may  disappear  without 

undergoing  the  intermediate  process  of  fusion, 
and  a mass  of  ice,  freely  exposed  to  the  air  on  a 
dry,  frosty  day,  loses  weight.  Steam,  therefore, 
rises  from  water  at  all  temperatures,  but  with 
more  rapidity  and  a higher  elastic  force  as  the 
temperature  is  higher. 

In  a vacuum  vapors  form  instantaneously. 
If  we  take  a barometer,  a a.  Fig.  25,  and  pass 
into  the  Torricellian  vacuum  which  exists  at  its 
upper  part  a small  quantity  of  sulphuric  ether, 
even  before  it  has  reached  the  void  space,  vapor 
forms,  and  the  mercury  is  instantly  depressed. 
Under  ordinary  circumstances,  when  the  instrument  is 
standing  at  30  inches,  the  column  at  once  falls  to  15  or  16, 
the  space  being  now  filled  with  the  vapor  of  ether ; and  if 
in  succession  other  liquids  are  tried,  the  same  general  result 
is  obtained — instantaneous  vaporization  ; but  the  amount 
of  vapor  set  free  is  different  in  the  different  cases. 

Diminution  of  atmospheric  pressure  is,  therefore,  favorable 
to  vaporization,  and  were  the  pressure  of  the  air  entirely  re- 
26.  moved,  there  are  many  liquids  which  would  as- 
sume a permanently  aerial  form.  Take  a glass 
tube.  A,  Fig.  26,  closed  at  one  end  and  open  at 
the  other,  and,  having  filled  it  with  water,  in- 
vert it  in  a cup,  B,  and  introduce  into  it  a little 
sulphuric  ether,  which  will  rise  to  «,  the  top  of 
the  tube.  The  apparatus  is  ne:g:  to  be  placed 
under  an  air-pump  receiver,  and  exhaustion  made  : 
the  ether  enters  into  ebullition,  and  gives  off  vapor  which  is 
quite  transparent.  As  long  as  the  reduction  of  pressure  con- 
tinues, the  ether  keeps  the  gaseous  form,  but  on  readmitting 
the  air,  it  returns  to  the  liquid  state.  By  increase  of  press- 
ure, as  well  as  by  diminution  of  temperature,  vapors  may 
be  reduced  to  the  liquid  condition. 

Though  the  law  that  vapors  occupy  more  space  than  the 
liquids  from  which  they  come  is  of  universal  application, 
the  increase  of  volume  is  by  no  means  the  same  in  all  cases. 

How  can  it  be  proved  that  vaporization  goes  on  at  all  temperatures  ? What 
is  the  eflfect  which  ensues  when  a vaporizable  liquid  is  passed  into  a Torri- 
cellian vacuum  ? What  substances  exist  commonly  in  the  liquid  state,  in  con- 
sequence of  the  pressure  of  the  air  ? What  is  the  effect  of  an  increased  press- 
ure on  vapors  ? Do  all  liquids  expand  equally  in  assuming  the  vaporous  state  ? 


CUMULATIVE  PRESSURES. 


45 


Under  ordinary  circumstances  of  pressure,  a cubic  inch  of 
water  at  its  boiling  point  produces  nearly  a cubic  foot  of 
steam,  or  1696  cubic  inched  more  accurately.  The  same 
quantity  of  alcohol  produces  519  cubic  inches,  and  of  oil  of 
turpentine  192  cubic  inches. 

The  elastic  force  exerted  by  vapors  under  certain  limits 
can  be  measured  by  the  apparatus  given  in  Fig.  25.  The 
theory  of  the  process  is  very  simple.  The  height  at  which 
the  barometer  stands  is  determined  by  the  pressure  of  the 
air.  In  the  experiment  there  described,  as  long  as  there  is 
nothing  to  counterbalance  that  pressure,  the  mercury  is 
forced  up  by  it  in  the  tube  to  a height  of  30  inches  ; but  on 
introducing  some  ether,  the  vapor  which  forms,  exerting  an 
elastic  force  in  the  opposite  direction,  tends  to  push  the  mer- 
cury out  of  the  tube.  On  the  one  hand,  we  have  the  press- 
ure of  the  air  ; on  the  other,  the  elastic  force  of  the  ethereal 
vapor ; they  press  in  opposite  directions*  and  the  resulting 
altitude  at  which  the  mercury  stands  expresses,  and,  indeed, 
measures  the  elastic  force  of  the  vapor.  Thus,  at  a tem- 
perature of  eighty  degrees,  water  will  depress  the  mercurial 
column  about  1 inch,  alcohol  about  2 inches,  and  sulphuric 
ether  about  20.  These  numbers,  therefore,  represent  the 
elastic  force  of  the  vapors  evolved. 

In  close  vessels,  from  which  there  is  no  escape,  or  where 
the  escape  is  greatly  retarded,  a constantly  Fig.  27. 
accumulated  force  is  generated  when  the 
temperature  is  raised.  Thus,  if  we  place 
some  water  in  a flask,  a.  Fig.  27,  into  which 
a tube,  b b,  is  inserted  air-tight  by  means  of 
a cork,  and  bent  in  the  form  exhibited  in  the 
figure,  and  dipping  nearly  to  the  bottom  of 
the  flask,  on  the  application  of  a spirit  lamp, 
the  vapor  generated,  having  no  passage  of 
escape,  accumulates  in  the  upper  part  of  the 
flask,  and,  exerting  its  elastic  force,  presses 
the  liquid  through  the  tube  in  a continuous  stream.  The 
mechanical  force  which  thus  arises,  when  every  avenue  of 
escape  is  stopped,  is  strikingly  exhibited  by  the  little  glass 
bulbs  called  candle  bombs  ; these  are  small  globules  of 
glass,  about  as  large  as  a pea,  with  a neck  an  inch  long ; 

How  can  the  elastic  force  of  vapors  be  measured  by  the  barometer  ? What 
is  the  principle  involved?  When  water  is  heated  in  a vessel  from  which 
the  steam  can  not  escape,  what  is  the  effect  ? How  may  this  be  illustrated  ? 


46 


RELATION  OF  VAPORS  TO  PRESSURE. 


into  the  interior  a drop  of  water  is  introduced,  and  the  term- 


Fig.  28. 




ination  of  the  neck  hermetically  sealed 
by  melting  the  glass.  When  one  of  these 
""  is  stuck  in  the  wick  of  a candle  or  lamp, 
as  in  Fig.  28,  the  heat  vaporizes  a por- 
tion of  the  water,  and  there  being  no 
passage  through  which  the  steam  can 
escape,  the  bulb  is  burst  to  pieces  with 
a loud  explosion;  a mechanical  force 
which  is  wonderful  when  we  consider  the 
amount  of  water  employed.  It  is  a miniature  representa- 
tion of  what  takes  place  on  the  large  scale  in  the  bursting 
of  high-pressure  steam-boilers. 

Marriotte’s  law,  the  law  which  assigns  the  volume  of 
a gas  under  variations  of  pressure,  applies,  under  certain  re- 
strictions, to  the  case  of  vapors.  A permanently  elastic  gas, 
when  the  pressure  is  doubled,  contracts  to  one  half  of  its 
former  volume  ; if  the  pressure  be  tripled,  to  one  third,  and 
so  on,  but  not  so  with  vapors ; if,  upon  steam,  as  it  rises 
from  water  at  212^,  any  increase  of  pressure  be  exerted,  this 
vapor  at  once  loses  its  elastic  form,  and  instantly  condenses 
into  water.  But  vapors,  like  atmospheric  air,  if  the  pressure 
upon  them  is  diminished,  follow  Marriotte’s  law ; thus,  if  the 
pressure  be  reduced  to  one  half,  steam  at  once  doubles  its 
volume.  For  vapors,  therefore,  Marriotte’s  law  holds  for 
diminutions  of  pressure,  but  in  other  instances,  when  the 
pressures  are  increased,  it  apparently  fails,  the  vapors  relaps- 
ing into  the  liquid  form. 

That  the  elasticity  of  a vapor  increases  with  its  ternper- 
Fig.2^.  21-ture,  may  be  readily  proved  by  taking  a tube  one 
third  of  an  inch  in  diameter  and  20  inches  long,  closed 
at  one  end  and  open  at  the  other,  a a.  Fig.  29,  with 
a jar,  b,  an  inch  or  more  in  diameter  and  20  inches 
deep.  Let  the  tube  be  filled  with  quicksilver,  so  as 
to  leave  a space  of  half  an  inch,  into  which  ether 
may  be  poured  ; invert  the  tube  in  the  deep  jar,  also 
containing  quicksilver ; the  ether  of  course  rises  to 
the  upper  closed  extremity.  If  now  the  tube  be  lift- 
ed in  the  jar  as  high  as  possible  without  admitting 
external  air,  a certain  portion  of  the  ether  will  va- 


What  is  Marriotte’s  law  ? Does  it  apply  in  the  case  of  vapors  under  a 
diminution  of  pressure  ? Does  it  apply  under  an  increase  ? What  relation 
is  there  between  elasticity  and  temperature  ? 


MEASURE  OF  ELASTIC  FORCE. 


47 


porize,  and,  depressing  the  quicksilver,  its  elastic  force  may 
be  measured  by  the  length  of  the  resulting  column.  If  now 
the  end  of  the  tube  be  grasped  in  the  hand,  or  if  it  be  slightly 
warmed  by  the  application  of  a lamp,  the  mercurial  column 
is  at  once  depressed,  proving  that  the  elastic  force  of  the 
vapor  is  increasing.  As  soon  as  the  tube  is  warmed  to  the 
boiling  point  of  the  ether,  the  column  of  mercury  is  depressed 
exactly  to  the  level  on  the  outside  of  the  tube.  At  this 
point,  therefore,  it  balances,  or  is  equal  to  the  pressure  of 
the  air. 

Now  let  the  tube  be  depressed  in  the  jar  ; it  will  be  seen 
with  what  facility  the  vapor  reassumes  the  liquid  condition. 
As  the  tube  descends,  the  vapor  condenses,  and  the  mercury 
keeps  constantly  at  the  same  level. 

Under  these  circumstances,  it  follows  that  the  vapor  is  at 
its  maximum  density.  We  can  not  increase  that  density  by 
bringing  pressure  to  bear  upon  it  by  depressing  the  tube,  for 
the  moment  the  attempt  is  made  the  vapor  liquefies. 

The  point  of  maximum  density  rises  with  the  temperature 
of  the  vapor.  The  density  of  air  at  212°  being  taken  at 
1000°,  that  of  the  vapor  of  water  at  its  maximum  density 
will  be  as  follows  : 


Table  of  the  Maximum  Density  of  Water-vajpor. 


Temperature. 

Density. 

Weight  of  100  Cubic  In, 

32"^ 

5-690  . 

•136  grains 

10-293 

•247 

14-108 

•338 

100® 

46-500 

1-113 

150® 

170-293 

4-076 

212® 

625-000 

14-962 

By  exerting  pressures  to  a sufficient  degree  on  various 
gases,  they  have  been  converted  into  liquid  bodies.  Sulphur- 
ous acid,  cyanogen,  chlorine,  carbonic  acid,  protoxide  of  ni- 
♦ trogen,  have  yielded  in  this  way.  But  hydrogen,  oxygen, 
and  nitrogen  may  be  exposed  to  pressures  of  50  atmospheres 
without  liquefying.  The  condensation  of  carbonic  acid  is 
sometimes  conducted  on  the  large  scale  in  strong  vessels  of 
wrought  iron.  If  the  resulting  liquid  is  allowed  to  escape 
into  the  air,  a portion  is  frozen  by  the  evaporation  of  the  rest. 


How  can  the  increase  of  elastic  force  under  these  circumstances  be  shown  ? 
At  the  boiling  point  of  a liquid,  what  is  the  elastic  force  of  its  vapor  equal 
to  ? What  is  meant  by  the  maximum  density  of  a vapor  ? How  can  it  be 
shown  that  vapors  thus  in  a Torricellian  void  are  at  the  maximum  density  ? 


48 


BOILING. 


and  a snowy,  solid  substance  is  the  result.  This,  moisten- 
ed with  sulphuric  ether,  will  depress  the  thermometer  tt 
—135° 


LECTURE  XL 

Ebullition. — Theory  of  Boiling. — In  Papin's  Digester 
Water  never  Boils. — Instantaneous  Condensation  of 
Vapors. — Effect  of  Variations  of  Pressure. — Effect  of 
Nature  of  the  Vessel. — Boiling  on  Mountains. — Effect 
of  Bed-hot  Surfaces. 

By  introducing  different  liquids  into  a tube,  arranged  as 
that  represented  in  Fig.  29,  we  can  prove  that  the  observa- 
tion holds  good  in  every  case,  that,  as  soon  as  the  boiling 
point  of  a liquid  is  reached,  the  elastic  force  of  the  vapor 
rising  from  it  is  equal  to  the  pressure  of  the  air. 

We  have  said  that  at  a temperature  of  80°,  the  vapor  of 
water  will  depress  the  mercurial  column  of  a barometer 
about  one  inch  ; but  if  the  temperature  be  raised  to  212°, 
the  mercury  is  at  once  depressed  to  the  level  in  the  cistern  ; 
at  that  temperature,  therefore,  the  elastic  force  of  the  vapor 
is  equal  to  the  pressure  of  the  air. 

Upon  these  principles,  the  phenomena  of  boiling  or  ebul- 
lition are  easily  explained.  When  the  temperature  of  a li- 
quid is  raised  sufficiently  high,  vapor  is  rapidly  generated 
from  those  portions  of  the  mass  which  are  hottest,  and  the 
violent  motion  characterized  by  the  term  “ boiling”  is  the 
result.  This  is  due  to  the  fact  that  the  elastic  force  of  the 
generated  vapor  at  that  point  is  equal  to  the  atmospheric 
pressure,  and  the  vapor  bubbles  expanding,  can  maintain 
themselves  in  the  liquid  without  being  crushed  in ; they  rise 
to  the  surface,  and  there  burst.  But,  just  before  ebullitioif 
takes  place,  a singing  sound  is  often  heard,  due  to  the  par- 
tial formation  of  bubbles,  which,  so  long  as  they  are  in  the 
neighborhood  of  the  hottest  part,  have  elasticity  enough  to 
maintain  their  form  ; but  the  moment  they  attempt  to  rise 
through  the  cooler  portion  of  the  liquid  just  above,  their  elas- 
ticity is  diminished  by  their  decline  of  temperature,  and  the 
atmospheric  pressure  crushing  them  in,  they  resume  the  li- 

At  the  boiling  point  of  water,  w^hat  is  the  elastic  force  of  its  steam  ? Ex- 
plain the  phenomena  of  boiling.  What  is  the  cause  of  the  singing  sound  ? 


BOILING. 


49 


quid  condition  ; for  a few  moments,  therefore,  while  the  va- 
por has  riot  gathered  elastic  force  enough  to  maintain  its 
condition  perfectly,  these  bubbles  are  transiently  formed  and 
disappear,  and  the  liquid  is  thrown  into  a vibratory  move- 
ment which  gives  rise  to  the  singing  sound. 

Water,  when  heated  in  a vessel  from  which  the  steam  can 
not  escape,  never  boils.  This  takes  place  in  the  interior  of 
Papin’s  digester,  which  is  a strong  metallic  vessel,  in  which 
water  is  inclosed,  and  the  orifice  through  which  it  was  in- 
troduced fastened  up.  As  the  steam  can  not  escape,  the 
water  can  not  boil,  no  matter  what  the  temperature  may  be. 
But  the  vapor  which  accumulates  in  the  interior  of  the  ves- 
sel exerts  an  enormous  pressure.  It  is  under  the  same  con- 
ditions as  were  considered  in  the  case  of  the  candle  bombs. 
Papin’s  digester  is  used  to  effect  the  solution  of  bodies  by 
water  which  are  not  acted  on  readily  by  that  liquid  at  its 
common  boiling  point. 

As  a vapor,  rising  from  a vaporizing  liquid,  will  bear  no 
increase  of  pressure,  so  neither  will  it  bear  any  reduction 
of  temperature  without  instantaneously  Fig.  30. 

condensing.  This  may  be  strikingly 
shown  by  an  arrangement  such  as  is 
represented  in  Fig.  3 0 . Into  the  mouth 
of  a flask,  a,  let  there  be  fitted  a tube, 

5,  half  an  inch  in  diameter,  and  bent, 
as  shown  in  the  figure.  Having  intro- 
duced a little  water  into  the  flask,  cause 
it  to  boil  rapidly  by  the  application  of 
a spirit  lamp  : the  steam  which  forms 
soon  drives  out  the  atmospheric  air  from 
the  flask  and  the  tube,  and  when  this  is  entirely  completed, 
and  the  vapor  issuing  abundantly  from  the  mouth  of  the 
tube,  plunge  the  end  of  the  tube  beneath  some  cold  water, 
contained  in  the  jar,  c,  and  take  away  the  lamp.  As  soon 
as  this  is  done,  the  cold  water,  condensing  the  steam  in  the 
tube,  rises  to  occupy  its  place,  and  presently  passing  over 
the  bend,  introduces  itself  with  surprising  violence  into  the 
interior  of  the  flask,  filling  it  entirely  full,  or,  which  more 
commonly  takes  .place,  breaking  it  to  pieces  with  the  force 
of  the  shock.  The  low-pressure  steam-engine  depends  on 

Why  does  water  heated  in  a close  vessel  never  boil  ? Describe  Papin’s 
digester.  What  is  its  use  ? Can  the  steam  of  boiling  water  be  cooled  with- 
out condensation?  Give  an  example  of  the  rapidity  of  its  condensation. 


50 


BOILING  IN  VACUO. 


this  fact  of  the  rapid  condensibility  of  vapor,  the  high-press^ 
ure  engine  on  its  elastic  force. 

Fig.  3L  The  principle  involved  in  the  action  of  the 

low-pressure  engine,  and  more  especially  that 
form  of  it  which  was  the  invention  of  New- 
comen, is  well  illustrated  by  the  instrument 
represented  in  Fig.  31.  It  consists  of  a glass 
tube,  blown  into  a bulb  at  its  lower  extrem- 
ity. In  the  bulb  some  water  is  placed,  and 
a piston  slides,  without  leakage,  in  the  tube. 
On  holding  the  bulb  in  the  flame  of  a spirit 
lamp,  steam  is  generated,  and  the  piston  forced 
upward.  On  dipping  it  into  a basin  of  cold 
water,  the  steam  condenses,  and  the  piston  is 
depressed ; and  this  action  may  be  repeated 
at  pleasure. 

As  the  pressure  of  the  atmosphere  determ- 
ines the  boiling  point  of  a liquid,  and  as  that  pressure  is 
variable,  the  boiling  point  is  not  fixed,  but  a variable  point. 
There  are  many  experiments  which  might  be  introduced 
Fig.  32.  as  proofs  of  this  fact.  If  a glass  of  warm  water 
be  placed  beneath  the  receiver  of  an  air  pump, 
as  in  Fig.  32,  when  the  rarefaction  has  reached 
a certain  point,  ebullition  sets  in,  and  the  water 
continues  to  boil  at  a lower  temperature  as  the 
exhaustion  is  more  perfect.  In  a vacuum,  water 
can  be  made  to  boil  at  32®. 

On  this  principle,  that  the  boiling  point  depends  on  the 
existing  pressure,  we  give  an  explanation  of  a curious  ex- 
periment, in  which  ebullition  is  apparently  brought  about 
Fig.  33.  by  the  application  of  cold  : Take  a Florence 
flask,  a,  Fig.  33,  and,  having  filled  it  half 
full  of  water,  cause  the  water  to  boil  violently, 
so  as  to  expel  all  the  atmospheric  air ; intro- 
duce a cork  which  will  fit  the  mouth  of  the 
flask  air-tight  a moment  after  it  is  moved 
from  the  lamp,  and  before  any  atmospheric 
air  has  been  introduced.  If  the  flask  be  now 
dipped  into  ajar,  b,  of  cold  water,  its  water  begins  to  boil, 

On  what  property  of  vapor  does  the  low-pressure  steam-engine  depend  ? 
On  what  the  high-pressure  ? How  may  it  be  proved  that  the  boiling-point 
depends  on  the  pressure  ? At  what  temperature  will  water  boil  in  vacuo  ? 
Explain  the  process  by  which  warm  water  may  be  made  to  boil  by  the  ap- 
plication of  cold. 


LiaUlDS  ON  RED-HOT  SURFACES. 


51 


and  will  continue  to  do  so  until  its  temperature  is  reduced 
quite  low.  The  cause  of  this  phenomenon  is  due  to  the  fact 
that  the  cold  water  condenses  the  steam  in  the  flask,  and  a 
partial  vacuum  is  the  result.  In  this  partial  vacuum  the 
water  boils,  as  in  the  experiment  illustrated  by  Fig.  32  ; 
and  the  steam,  as  fast  as  it  is  generated,  is  condensed  by  the 
cold  sides  of  the  flask. 

Besides  this  variation  of  the  boiling  point  under  variation 
of  pressure,  the  nature  of  the  vessel  in  which  the  process  is 
carried  forward  exerts  a certain  action  ; thus,  in  a polished 
glass  vessel,  the  boiling  point  is  214°,  but  in  a rough  metal 
vessel  it  is  212*^.  If  the  glass  has  been  carefully  cleaned 
with  hot  sulphuric  acid,  water  may  be  heated  to  221°  with- 
out ebullition  ; and,  on  the  contrary,  if  coated  with  a film 
of  shell-lac,  the  boiling  point  will  be  211°. 

Some  travelers  report,  Aiat  in  certain  mountainous  regions 
meat  can  not  be  cooked  by  the  ordinary  process  of  boiling. 
As  we  ascend  to  elevated  regions  in  the  air,  the  atmospheric 
pressure  becomes  less,  because  the  column  of  air  above  is 
shorter,  and  therefore  there  is  less  air  to  press.  Under  such 
circumstances,  the  boiling  point  of  water  of  course  descends, 
and  may  possibly  become  so  low  as  to  bring  about  the  spe- 
cific change  required  in  the  cooking  of  meat.  An  ascent 
through  530  feet  lowers  the  boiling  point  one  degree.  Upon 
this  principle  we  can  determine  the  altitude  of  accessible 
elevations,  by  determining  the  thermometric  point  at  which 
water  boils  upon  them.  A peculiar  thermometer,  called  the 
hypsometer,  has  been  invented  for  this  purpose. 

When  a drop  of  water  is  placed  on  a red-hot  polished  sur- 
face of  platinum,  it  does  not,  as  might  be  expected,  com- 
mence to  boil  rapidly,  but  remains  perfectly  quiescent,  gath- 
ering itself  up  into  a globule.  If  the  platinum  be  now  al 
lowed  to  cool,  as  soon  as  its  temperature  has  reached  a 
point  at  which  it  has  ceased  to  be  visibly  hot,  the  drop  of 
water  is  suddenly  dissipated  in  a burst  of  steam.  The  ex 
planation  given  of  this  phenomenon  is,  that  at  the  high 
temperature  the  drop  is  not  fairly  in  contact  with  the  red- 
hot  surface,  but  a stratum  of  steam  intervenes  ; this,  being 

How  does  the  nature  of  the  vessel  affect  the  boiling  point  ? Why  is  it 
probable  that  meat  can  not  be  cooked  on  high  mountains  ? How  high  must 
we  ascend  to  bring  the  boiling  point  to  211°?  How  may  the  altitude  of 
mountains  be  determined  by  the  thermometer  ? What  are  the  phenomena 
exhibited  by  water  in  contact  with  red-hot  platinum  ? What  is  the  sup- 
posed explanation  ? 


52 


THE  BOILING  POINT. 


a bad  conductor,  prevents  ebullition  from  occurring,  but  as 
soon  as  the  temperature  declines,  and  this  steam  no  longer 
props  up  the  drop,  an  explosive  ebullition  ensues,  because 
of  the  contact  which  has  taken  place.  This  condition  is 
known  as  the  spheroidal  state  of  a liquid.  Water  enters 
upon  it  at  temperatures  between  288°  and  340°  of  the  hot 
surface,  its  own  temperature  being  about  206°.  It  is  said 
to  be  in  consequence  of  this  want  of  actual  contact  that  the 
hand  can  be  passed  through  red-hot  and  molten  metal  with- 
out being  burned. 

I 

I 

! 

LECTURE  XII. 

Vaporization. — The  Boiling  Point  rises  with  the  Press- 
ure. — Relation  hetioeen  sensible  and  insensible  Heat. — 
The  Cryophorus. — Leslie's  Process  for  freezing  Water. 
— Variability  of  Moisture  in  the  Air. — Hygrometers. 
— Method  of  the  Dew  Point. 

Under  an  increase  of  pressure,  the  boiling  point  rises, 
and  the  elastic  force  of  the  steam  evolved  becomes  corre- 
spondingly greater.  As  we  have  seen,  the  elastic  force  of 
steam  from  water  boiling  at  212°  is  equal  to  the  pressure 
of  one  atmosphere  ; but  if  the  pressure  be  doubled,  the  boil- 
ing point  rises  to  250°  ; if  quadrupled,  to  294°  ; and  under 
a pressure  of  fifty  atmospheres,  it  is  more  than.  500°. 

These  results  may  be  established  by  the 
aid  of  the  boiler,  represented  in  Fig.  34,  a. 
It  is  a globular  vessel  of  brass,  and  is  about 
three  inches  in  diameter.  In  its  upper  part 
are  three  perforations,  into  one  of  which  the 
stop-oock,  b,  is  screwed ; through  the  second 
a tube,  c,  is  inserted,  deep  enough  to  reach 
nearly  to  the  bottom  of  the  boiler ; and  through 
the  third  a thermometer,  d,  is  introduced. 
Some  quicksilver  is  poured  in,  sufficient  to 
cover  the  end  of  the  tube,  c,  half  an  inch  or 
more  deep,  and  upon  it  water  is  poured,  the 
bulb  of  the  thermometer  being  immersed  in  it.  The  stop- 
cock, h,  being  open,  a spirit  lamp  is  applied  to  bring  the 

How  is  the  boiling  point  affected  by  an  increased  pressure  ? Describe 
the  boiler.  Fig.  34,  and  its_use. 


LATENT  HEAT  OF  VAPORS. 


53 


water  to  its  boiling  point,  and  as  the  steam  can  freely  pass 
out,  this  of  course  takes  place  at  212^.  On  closing  the 
stop-cock,  the  steam  can  no  longer  escape,  but,  exert’ng  its 
elastic  force  on  the  surface  of  the  boiling  liquid,  presses  the 
mercury  up  in  the  tube,  c.  The  altitude  of  the  mercu  ;ial 
column  measures  the  amount  of  this  pressure,  and  the  ther- 
mometer indicates  the  corresponding  change  in  the  boiling 
point : as  soon  as  the  pressure  is  equal  to  two  atmospheres, 
the  thermometer  will  be  found  to  have  risen  to  250^. 

It  is  immaterial  at  what  temperature  vaporization  is  car- 
ried on,  a very  large  amount  of  heat  must  always  be  ren- 
dered latent ; and,  in  point  of  fact,  vapors  generated  at  a 
low  temperature  contain  more  latent  heat  than  those  gen- 
erated at  a high  one.  The  relation  which  exists  in  the 
amount  of  heat  rendered  latent  at  different  temperatures  is 
very  simple.  The  sum  of  the  insensible  and  sensible  heat  is 
always  the  same;  thus,  water  boiling  at  212°  absorbs  1000° 
of  latent  heat,  the  sum  of  the  two  quantities  being  of  course 
1212  ; but  vapor  rising  from  water  at  32°  contains  of  latent 
heat  1 180°  ; here,  again,  the  sum  of  the  two  quantities  is 
1212°  ; and  the  same  observation  holds  for  intermediate 
temperatures. 

When  vapors  return  to  the  liquid  condition,  the  heat  which 
has  been  latent  in  them  reassumes  the  sensible  form.  They 
may  thus  be  regarded  as  containing  a great  store  of  caloric, 
of  the  effects  of  which  many  natural  phenomena  furnish  us 
with  striking  examples.  Thus,  there  is  a remarkable  dif- 
ference between  the  climate  of  the  eastern  coast  of  America 
and  the  opposite  European  coasts  in  the  same  latitude,  and 
this  arises  from  the  action  of  the  Gulf  Stream,  a great  stream 
of  warm  water,  which,  issuing  from  the  Gulf  of  Mexico,  and 
passing  the  Atlantic  States,  stretches  across  toward  the  Eu- 
ropean Continent.  The  vapors  which  arise  from  it  give 
forth  their  latent  heat  to  the  air,  and  the  southwest  winds, 
which  are  therefore  damp  and  warm,  moderate  the  climates 
of  those  countries. 

I^he  cryophorus,  or  frost  bearer,  an  instrument  invented 
by  Dr.  Wollaston,  in  which  water  may  be  frozen  by  the  cold 
produced  by  its  own  evaporation,  depends  for  its  action  on 

Do  vapors  generated  at  low  or  high  temperatures  contain  most  latent  heat? 
What  relation  is  there  between  the  insensible  and  sensible  heats  of  vapors 
at  different  temperatures  ? When  a vapor  condenses,  what  becomes  of  its 
latent  heat?  What  effect  has  the  Gulf  Stream  on  the  climate  of  Europe? 
Explain  the  cause  of  it. 


54 


THE  CRYOPHORUS. 


Fig.  35.  the  laws  relating  to  latent  heat.  It  is  represented 
in  Fig.  35,  and  consists  of  a bent  tube,  c,  half  an 
inch  or  more  in  diameter,  with  a bulb,  a and  b,  at 
each  of  the  extremities ; the  upper  bulb,  b,  is  filled 
one  third  with  water,  and  the  rest  of  the  space, 
with  the  tube,  c,  and  the  other  bulb,  a,  is  free  from 
atmospheric  air,  and  occupied  by  the  vapor  of  wa- 
ter only.  If  now  the  bulb  a be  immersed  in  a 
freezing  mixture  of  nitric  acid  and  snow,  although 
the  tube,  c,  may  be  of  considerable  length,  the  wa- 
ter in  the  distant  bulb,  5,  presently  freezes  ; hence 
the  name  of  the  instrurhent,  frost  bearer,  because  cold  ap- 
plied at  one  point  produces  a freezing  effect  at  another, 
which  is  at  a considerable  distance.  The  action  of  the  in- 
strument is  simple  : in  the  cold  bulb,  a,  which  is  in  contact 
with  the  freezing  mixture,  the  vapor  is  condensed ; fresh 
quantities  rise  with  rapidity  from  the  water  in  the  other 
bulb,  to  be  in  their  turn  condensed ; a continual  condensa- 
tion, therefore,  goes  on  in  a,  and  a continual  evaporation  in 
5,  but  the  vapor  thus  formed  in  b must  have  caloric  of  elas- 
ticity ; it  obtains  it  from  the  water  from  which  it  is  rising, 
the  temperature  of  which  therefore  descends  until  solidifica- 
tion takes  place. 

Leslie’s  process  for  freezing  water  in  vacuo  by  its  own 
evaporation  is  an  example  of  the  same  kind.  If  some  water 
in  a watch-glass  is  placed  in  an  exhausted  receiver,  with  a 
large  surface  of  sulphuric  acid,  as  fast  as  vapor  rises  it  is 
condensed  by  the  acid ; a rapid  evaporation 
of  the  water  therefore  takes  place,  the  tem- 
perature falls,  and  congelation  finally  en- 
sues. In  Fig.  36  this  apparatus  is  repre- 
sented ; a is  the  watch-glass  containing 
water,  h a wide  dish  filled  with  sulphuric 
acid,  and  c a low  bell  jar  in  which  the  exhaustion  is  made. 

A drop  of  prussic  acid  held  in  the  air  on  the  tip  of  a rod 
solidifies,  the  portion  that  evaporates  obtaining  its  latent 
heat  from  the  portion  left  behind,  and  on  the  same  principle 
liquid  carbonic  acid~“can  also  be  solidified. 

The  amount  of  watery  vapor  contained  in  the  air  is  very 
variable.  Many  common  facts  prove  this  : the  swelling  of 


Fig.  36. 


Pescribe  the  cryophorus.  What  is  the  reason  that  cold  applied  to  one 
bulb  freezes  water  in  the  other?  Describe  Leslie’s  process  for  freezing 
water  in  vaciio  ? Why  does  a drop  of  prussic  acid  held  in  the  air  solidify  ? 


HYGROMETERS. 


55 


wooden  furniture  takes  place  in  consequence  of  damp  weath- 
er ; and  the  opposite  effect,  or  its  shrinking,  occurs  during 
dry.  Several  instruments  have  been  invented  to  determine 
what  the  amount  is  at  any  time  ; they  are  called  hygrom- 
eters. In  one  of  these,  the  relative  dampness  or  dryness  of 
the  atmosphere  is  determined  by  the  stretching  or  contract- 
ing of  a hair,  which  is  very  sensitive  to  such  changes.  A 
general  idea  of  such  an  instrument  may  be  obtained  by  con- 
sidering the  metallic  bar  of  the  pyrometer.  Fig.  15,  to  be  re- 
placed by  a hair,  the  movements  of  which  would  of  course 
be  communicated  to  the  index ; in  another  a slip  ef  whale- 
bone is  used  instead  of  the  hair.  • 

Saussure’s  hygrometer,  which  is  constructed  on  these  prin- 
ciples, has  been  very  extensively  used.  It  consists 
of  a human  hair  eight  or  ten  inches  long,  b c.  Fig. 

37,  fastened  at  one  extremity  to  a screw,  a,  and  at 
the  other  passing  over  a pulley,  c,  being  strained 
tight  by  a silk  thread  and  weight,  d.  From  the 
pulley  there  goes  an  index,  which  plays  over  the 
graduated  scale,  e e\  so  that,  as  the  pulley  turns 
through  the  shortening  or  lengthening  of  the  hair, 
the  index  moves.  The  instrument  is  graduated 
to  correspond  with  others  by  first  placing  it  under 
a bell  jar,  with  a dish  of  sulphuric  acid  or  other 
substance  having  an  affinity  for  water,  which,  ab- 
sorbing all  the  moisture  of  the  air  of  the  bell,  brings  it  to 
absolute  dryness.  The  point  at  which  the  index  then  stands 
is  marked  0.  The  hygrometer  is  next  placed  in  a jar,  the 
interior  of  which  is  moistened  with  water  ; when  the  index 
has  again  become  stationary,  the  point  is  marked  100°,  and 
the  intervening  space  divided  into  100  equal  parts. 

The  hair  should  have  its  oily  matter  removed  by  soaking 
in  sulphuric  ether.  This  preparation  renders  it  much  more 
sensitive. 

There  is  a simple  and  ingenious  instrument,  the  move- 
ments of  which  depend  on  these  prin-  3g 

ciples  ; it  is  represented  in  Fig.  38  : a g, 

a thin  slip  of  pine  wood,  a a,  cut  across 
the  grain,  a foot  long  and  an  inch  wide, 

has  inserted  into  its  corners  four  needles,  all  pointing  in  one 

How  can  it  be  proved  that  the  amount  of  moisture  in  the  air  is  variable  ? 
"What  is  the  hygrometer  ? Describe  the  hair  hygrometer.  Describe  the  in- 
strument, Fig.  38. 


56 


THE  DEW  POINT. 


direction  backward  ; if  this  instrument  be  set  upon  a floor 
or  flat  table,  in  the  course  of  time  it  will  crawl  a consider- 
able distance.  During  dry  weather  the  thin  board  contracts, 
and  the  two  fore  legs  taking  hold  of  the  table,  the  hind  ones 
are  drawn  up  a little  space  ; when  the  weather  turns  damp, 
the  board  expands,  and  now  the  hind  legs,  pressing  against 
the  table,  cause  the  fore  ones  to  advance.  Every  change 
from  dry  to  damp,  or  the  reverse,  produces,  a walking  motion 
in  a continuous  direction,  and  the  distance  passed  over  is  a 
register  of  the  sum  total  of  these  changes. 

But  of  all  these  hygrometric  methods,  the  process  known 
as  “ the  determination  of  the  dew  point”  is  by  far  the  most 
philosophical.  This  method  consists  in  cooling  the  air  until 
it  begins  to  deposit  moisture.  When  there  is  much  moisture 
in  the  air,  it  obviously  requires  but  a slight  diminution  of 
temperature  to  cause  a portion  of  the  vapor  to  deposit  as  a 
Jew ; but  when  the  air  is  dryer,  the  cooling  must  be  carried 
to  a greater  extent.  The  precise  thermometric  point  at 
which  the  moisture  begins  to  deposit  is  called  the  dew  point. 

Thus,  if  we  take  a thin  metallic  vessel  containing  water, 
and  cool  it  gradually  by  the  addition  of  a mixture  of  nitrate 

of  potash  and  sal  ammoni- 
ac, or  any  of  the  cooling 
mixtures,  continually  stir- 
ring with  the  bulb  of  a 
small  thermometer,  as  soon 
as  the  temperature  has 
reached  a certain  point  a 
dew  is  deposited  on  the 
outside  of  the  metallic  ves- 
sel ; that  temperature  is 
the  dew  point  for  the  time 
being.  Knowing  the  tem- 
perature of  the  air,  the 
dew  point,  and  the  baro- 
metric pressure,  the  abso- 
lute amount  of  vapor  can 
be  determined  by  a simple 
calculation. 

DanielFs  hygrometer  ^if- 
fords  a ready  and  beautiful  method  of  determining  the  dew 

^ What  is  meant  by  the  “ dew  point  ?”  What  is  tho  process  for  ascertain- 
ing it  ? 


Fi^.  39. 


SPECIFIC  GRAVITY  OP  VAPORS. 


57 


Fig.  40. 


point.  It  consists  of  a cryophorus,  a c b,  Fig.  39,  the  bulb 
b being  made  of  black  glass,  and  a covered  over  with  mus- 
lin. The  bulb  b contains  ether  instead  of  water,  and  into 
it  there  dips  a very  delicate  thermometer,  cl.  Usually,  an- 
other thermometer  is  affixed  to  the  stand  of  the  instrument. 
When  a little  ether  is  poured  on  a,  by  its  evaporation  it 
cools  that  bulb,  and  ether  distils  over  from  b,  which,  of 
course,  also  becomes  cold.  After  a time,  the  temperature  of 
b sinks  to  the  dew  point,  and  that  bulb  becomes  covered 
with  a dew.  The  thermometer,  dy  then  shows  at  what  tem- 
perature this  takes  place,  and  of  course  gives  the  dew  point. 

The  PsYCHROMETER,  or  wet  bulb  hygrometer,  consists  of 
two  mercurial  thermometers  which  exactly  correspond  ; the 
bulb  of  one  of  them,  A,  Fig.  40,  is  covered 
with  muslin,  and  kept  constantly  wet  by  water 
supplied  by  a thread  from  a reservoir,  W.  The 
bulb,  B,  of  the  other  is  left  naked.  Owing  to 
the  evaporation  from  the  wet  bulb,  its  temper- 
ature will  be  lower  than  the  dry  one,  and  this 
in  proportion  to  the  rate  of  evaporation  or  the 
dryness  of  the  adjacent  air.  As  soon  as  the 
air  round  the  bulb  is  saturated  with  moisture, 
the  point  at  which  the  mercury  stands  is  the 
dew  point.  If  both  thermometers,  the  wet  and 
the  dry,  coincide,  the  air  contains  moisture  at 
its  maximum  density ; and  the  greater  the  difference  be- 
tween them,  the  dryer  the  air. 

It  is  frequently  necessary  to  remove  moisture  from  air  or 
gaseous  substances.  This  may  be  done  by  conducting  them 
through  tubes  containing  bodies  hav- 
ing a strong  attraction  for  water, 
such  as  chloride  of  calcium,  sulphu- 
ric or  phosphoric  acids.  Such  an 
arrangement  is  shown  in  Fig.  41, 
in  which  is  the  flask  in  which  the 
gas  is  generated,  b a bent  tube  con- 
necting with  the  drying  tube,  c, 
which  is  filled  with  fragments  of  chloride  of  calcium,  or 
pieces  of  glass  moistened  with  concentrated  sulphuric  acid. 
The  gas  escapes  dry  from  the  tube  d. 


Fig.  41. 


Describe  Daniell’s  hygrometer  and  the  mode  of  using  it.  Describe  the 
process  for  drying  gases. 

C 2 


58 


SPECIFIC  GRAVITY  OP  VAPORS. 


LECTURE  XIII. 

Evaporation  and  Interstitial  Radiation. — Methods  of 
Gay-Lussac  and  Lumas  for  ascertaining  the  Specific 
Gravity  of  Vapors. — Phenomena  of  Evaporation. — 
Control  of  Temperature^ — Effect  of  Dryness^  Stillness, 
Pressure,  and  Surface.— Evaporation  a Cooling'  Pro- 
cess.— Conduction  of  Solids. — Difference  among  differ- 
ent Metals. — -Rumford's  Experiments. 

The  specific  gravity  of  vapors  may  be  determined  in  sev- 
Fig.  42.  eral  ways.  The  following  is  the  method  of  Gay- 
Lussac  : A graduated  j ar,  a,  is  inverted  in  a basin 
of  mercury,  c,  which  rests  upon  a small  furnace. 
A glass  bulb  is  to  be  filled  quite  full  with  the  li- 
quid under  examination,  and  the  quantity  intro- 
duced is  accurately  weighed.  The  bulb  is  now 
slipped  into  the  jar,  a,  and  rises  to  its  top.  A cyl- 
inder, b,  open  at  both  ends,  but  the  lower  pressed 
down  into  the  mercury,  is  next  placed  round  a, 
and  the  interval  hlled  with  clear  oil.  The  fur- 
nace is  now  lighted  ; the  oil  and  the  mercury  be- 
come warm ; the  bulb  at  last  bursts,  and,  as  its 
vapor  depresses  the  mercury  in  the  graduated 
j ar,  its  volume  may  be  determined.  Thus,  know- 
ing the  weight  of  the  liquid,  the  volume  of  its  vapor,  and 
the  temperature  of  the  oil,  we  can  easily  calculate  the  vol- 
ume at  32°,  and  from  that  deduce  the  specific  gravity. 

The  method  of  Dumas  consists  in  weighing  a glass  globe 
filled  with  the  vapor  to  be  tried.  A portion  of  the  sub- 
stance is  to  be  introduced  into  the  globe,  the  weight  of  which 
is  first  determined,  and  this  is  then  held,  as  shown  in  the 
figure,  in  a bath  of  fusible  metal  placed  over  a small  fur- 
nace. The  heat  of  the  melted  metal  vaporizes  the  sub- 
stance, drives  out  the  air,  and  occupies  the  whole  cavity  in 
a state  of  purity.  When  no  more  vapor  escapes  from  the 
end  of  the  tube,  it  is  sealed  by  the  blow-pipe,  and  the  tem- 
perature of  the  bath  ascertained.  The  globe  is  now  to  be 

Describe  Gay-Lussac’s  method  of  determining  the  specific  gravity  of  a 
vapor.  Describe  the  method  of  Dumas. 


SPECIFIC  GRAVITY  OP  VAPORS. 


59 


carefully  weighed,  when  cold,  a second  time,  and  the  point 
of  the  tube  is  then  broken  under  quicksilver,  which  rises  and 
fills  it  complete- 
ly, and  this  be- 
ing subsequent- 
ly emptied  in- 
to a graduated 
j ar,  the  volume 
of  the  globe 
is  ascertained. 

Knowing  the 
volume  of  the 
globe,  we  know 
the  weight  of 
the  air  it  con- 
tains, and  this, 
subtracted  from 
the  first  weight, 
is  the  weight  of  the  glass  when  empty.  Subtracting  this 
again  from  the  second  weighing,  gives  us  the  weight  of  the 
vapor ; and  as  the  air  and  the  vapor  occupied  the  same 
volume,  their  densities  are  as  their  weights.  But,  as  their 
temperature  was  different,  a farther  calculation  is  required 
to  bring  them  to  the  same  standard. 

There  are  several  conditions  which  exert  a control  over 
the  rapidity  of  evaporation.  The  amount  of  vapor  which 
can  exist  in  a given  space  depends  entirely  on  the  tempera- 
ture. Thus  the  air  included  in  a glass  jar  which  is  stand- 
ing over  water  contains,  at  32^,  a certain  quantity  of  vapor  ; 
but  if  the  temperature  rises  to  60^,  it  contains  more,  and 
still  more  if  it  rises  to  90^.  Should  the  temperature  de- 
scend, a part  of  the  vapor  is  deposited  as  a mist.  The  quan- 
tity that  remains  in  suspension  is  determined  by  the  tem- 
perature alone. 

It  is  the  application  of  this  principle  which  constitutes 
the  most  beautiful  part  of  Watt’s  great  invention,  the  low- 
pressure  steam-engine.  Taking  advantage  of  the  fact  that 
the  quantity  of  vapor  which  can  exist  in  a given  space  is 
determined  by  the  lowness  of  temperature  of  any  portion  of 
it,  he  arranged  a vessel,  maintained  uniformly  at  a low  tem- 
perature, in  connection  with  the  cylinder  of  the  engine,  and 

What  is  it  that  regulates  the  quantity  of  vapor  in  a given  space  ? On 
what  principle  does  the  steam-engine  condenser  depend  ? 


60 


CAUSES  CONTROLLING  EVAPORATION 


thus  reached  the  apparently  paradoxical  result  of  condensing 
the  steam  without  cooling  the  cylinder. 

Among  other  causes  exerting  a control  over  evaporation 
in  the  air  is  the  dry  or  damp  state  of  that  medium.  As  is 
well  known,  evaporation  goes  on  V'lith  rapidity  when  the 
weather  is  dry,  and  is  greatly  retarded  when  the  weather 
is  damp.  So,  too,  a movement  or  current  exerts  a great  ef- 
fect. When  the  wind  is  blowing,  water  will  evaporate  much 
more  quickly  than  when  the  £iir  is  quite  calm  ; this  obvious- 
ly depends  on  a constant  renewal  of  surfaces,  so  that  as  fast 
as  one  portion  of  air  becomes  moist  it  is  removed,  and  a 
dryer  portion  takes  its  place.  Extent  of  surface  operates  in 
the  same  way ; the  same  quantity  of  water  will  evaporate 
much  more  rapidly  if  exposed  in  a plate  than  if  exposed  in 
a cup.  Pressure  also  exerts  a great  control ; for,  as  we  have 
seen,  evaporation  takes  place  instantaneously  in  a vacuum. 

While,  therefore,  there  are  several  circumstances  which 
can  control  the  rate  of  evaporation,  it  is  temperature  alone 
which  regulates  the  absolute  and  final  amount.  As  we 
have  just  seen,  a fixed  quantity  of  vapor  can  exist  in  a cer- 
tain space  at  a given  temperature ; and  it  matters  not  wheth- 
er that  space  is  full  of  atmospheric  air  or  is  a vacuum,  the 
absolute  quantity  will  be  precisely  the  same. 

At  one  time  it  was  supposed  that  evaporation  was  due  to 
a solvent  power  in  the  air — a kind  of  attraction  between 
that  medium  and  the  water  with  which  it  is  in  contact ; 
but  it  is  clear  that  such  an  opinion  is  wholly  untenable,  for 
the  process  goes  forward  with  the  greatest  rapidity  in  a 
vacuum,  when  the  air  is  totally  removed. 

Although  the  evaporation  of  liquids,  such  as  water,  will 
take  place  at  very  low  temperatures,  there-  is  reason  to  be- 
lieve that  the  process  has  a limit ; thus,  a minute  quantity 
of  vapor  will  rise  from  quicksilver  at  a temperature  of  60°, 
but  at  40°  not  a trace  can  be  discovered. 

All  processes  of  evaporation  are  cooling  processes,  because 
the  vapor  developed  requires  latent  heat  to  give  it  the  elas- 
tic form.  For  this  reason,  when  any  vaporizable  liquid,  as 
ether,  is  poured  on  the  bulb  of  an  air  thermometer,  or  on 
the  hand,  cold  is  produced. 

"What  effect  have  dryness  or  dampness  over  evaporation?  What  is  the 
effect  of  a current  ? What  of  extent  of  surface  ? What  of  pressure  ? What 
of  temperature  ? Does  evaporation  arise  from  a solvent  power  in  the  air  ? 
Is  there  any  limit  to  evaporation  ? Why  are  processes  of  evaporation  cool- 
ing processes  ? 


CONDUCTION. 


61 


The  pulse  glass  is  an  instrument  which  may  serve  as  an 
illustration : it  consists  of  a glass  Fig.  44. 

tube,  bent  twice  at  right  angles, 
and  terminated  by  bulbs,  as  in 
Fig.  44.  It  is  partially  filled 
with  spirit  of  wine,  the  rest  be- 
ing occupied  by  the  vapor  of  that  substance.  On  grasping 
one  of  the  bulbs  in  the  hand,  the  warmth  is  sufficient  to 
boil  the  liquid ; and  as  it  distills  over  into  the  other  bulb, 
an  impression  of  cold  is  felt. 


Interstitial  Uadiation  or  Conduction. 


We  now  come  to  the  consideration  of  the  mode  by  which 
heat  is  transmitted  through  bodies,  or  interstitial  radiation, 
called  by  many  writers  conduction ; a term  involving  the 
idea  that  the  particles  of  bodies  are  in  actual  contact,  where- 
as it  has  been  abundantly  proved  that  they  are  separated 
from  each  other  by  interstices.  The  passage  of  the  heat 
across  these  spaces  is  what  is  meant  by  interstitial  radiation. 
From  the  currency  which  it  has  obtained,  and  the  conve- 
nience of  the  expression,  I shall  continue  to  use  the  word 

conduction.  , i rr 

Different  solids  conduct  heat  with  different  degrees  ot  la- 
cility.  If  we  take  a cylindrical  mass  of  metal,  and  hold 
tightly  against  its  surface  a piece  of  white  writing  paper, 
the  paper  may  be  placed  in  the  flame  of  a spirit  lamp  for  a 
considerable  time  without  scorching  ; but  if  we  take  a cy- 
lindrical piece  of  wood  of  the  same  dimensions,  and,  wrap- 
pino^  the  paper  round  it,  expose  it  to  the  flame,  it  rapidly 
scorches.  The  metal,  therefore,  keeps  the  paper  cool  by 
carrying  off  its  heat,  but  the  wood,  being  a bad  conductor, 

suffers  the  paper  to  burn.  . ^ i 

By  the  aid  of  the  apparatus  of  Ingenhouse,  Fig.  45,  the 
same  fact  may  be  proved  in  a more  general  45. 

way.  It  consists  of  a trough  of  brass  six 
inches  or  more  long,  three  wide,  and  three 
• deep  ; from  the  front  of  it  project  cylinders 
of  metallic  and  other  substances  of  the  same 
length  and  diameter ; they  may  be  of  silver, 
copper,  brass,  iron,  porcelain,  wood,  &c.,  in  succession  ; the 


Describe  the  pulse  glass.  What  is  interstitial  V ^ 

auction  ? How  may  it  be  proved  that  wood  and  metals  conduct  with  differ- 
ent degrees  of  facility  ? Describe  the  apparatus  of  Ingenhouse  . 


62 


CONDUCTION  OP  HEAT. 


surface  of  each  cylinder  is  smeared  with  bees’  wax.  On 
pouring  boiling  water  into  the  trough,  the  heat  passes  along 
these  cylinders  with  a rapidity  corresponding  to  their  con- 
ducting power,  and  the  wax  correspondingly  melts.  On  the 
silver  bar  the  wax  melts  most  rapidly,  and  on  the  wood 
most  slowly  ; on  the  others  intermediately ; thus  affording 
a clear  proof  that  different  solids  conduct  heat  with  different 
degrees  of  facility. 

Even  among  metallic  substances  great  differences  in  this 
Fig.  46.  respect  exist,  as  may  be  strikingly  shown  by 
the  instrument.  Fig.  46.  Into  a solid  ball 
of  copper,  a,  three  wires  of  equal  length  and 
equal  diameter  are  screwed — they  may  be 
, c copper,  brass,  and  iron  respectively : they 
are  flattened  at  their  farther  extremities, 
h,  c,  di  so  as  to  afford  a place  on  which  pieces 
of  phosphorus  may  be  put.  A lighted  spirit 
lamp  is  now  set  beneath  the  central  ball, 
the  temperature  of  which  soon  rises,  and  the  heat  passes 
with  different  degrees  of  speed  along  the  metals ; very  soon 
the  piece  of  phosphorus  at  the  end  of  the  copper  takes  fire ; 
then,  some  time  after,  follows  that  on  the  brass ; and  last, 
that  on  the  iron ; enabling  us  to  prove  to  persons  at  a dis- 
tance the  fact  that  these  different  metals  conduct  heat  with 
different  degrees  of  facility. 


Table  of  Conducting  Power  of  Solids. 


Gold  . . . . 

. . 1000 

Tin  . . . . 

. . 303*9 

Silver  . . . 

. . 973 

Lead  . . . . 

. . 179*6 

Copper  . . . 

. . 898 

Marble  . . . 

Iron  . . . . 

. . 374*3 

Porcelain  . . 

. . 14*2 

Zinc  . . . . 

. . 363 

Clay  . . . . 

. . 11*4 

If  a piece  of  wire  gauze  be  held  over  the  flame  of  a can- 
dle or  gas  jet.  Fig.  47,  the  flame  fails  to  pass  through  ; but 
the  gaseous  matter  of  which  the  flame  consists  freely  escapes 
through  the  meshes  of  the  gauze,  for  it  may  be  set  on  fire,  as 
shown  in  the  figure.  Flame  is  gaseous  matter,  or  solid 
matter  in  a state  of  excessive  subdivision,  temporarily  sus- 
pended in  gas,  brought  to  a very  high  temperature.  It  can 
not. ‘therefore,  pass  through  a piece  of  wire  gauze,  because 


What  does  it  prove  ? Are  there  differences  in  the  conducting  powers 
of  metals  ? How  may  that  be  proved  ? Can  the  flame  of  a candle  pass 
through  a piece  of  wire  gauze  ? 


CONDUCTING  POWER  OF  METALS. 


63 


the  metallic  threads,  exerting  a high  con- 
ducting power,  abstract  its  heat  from  the 
incandescent  gas>  and  bring  its  temperature 
down  to  a point  at  which  it  ceases  to  be 
luminous.  The  safety-lamp  of  Davy  is  an 
application  of  this  principle  ; by  it  combus- 
tion is  prevented  from  spreading  through 
Fij.  48.  masses  of  explosive  gas,  by  call- 
ing into  action  the  conducting 
power  of  a metallic  gauze,  with 
which  the  lamp  frame  is  sur- 
rounded, as  in  48.  The  safety-tube  of  Hem- 
mings,  used  to  prevent  explosions  in  the  ^ oxy hy- 
drogen blow-pipe,  acts  on  the  same  principle. 

Count  Rumford  made  several  experiments  to 
determine  the  conducting  power  of  those  vari- 
ous materials  which  are  used  for  the  purpose  of 
clothing.  He  placed  the  bulb  of  a thermometer 
in  the  centre  of  a spherical  glass  globe  of  larger 
diameter,  and  filled  the  interspace  with  the  sub- 
stances to  be  tried.  Having  immersed  the  ap- 
paratus in  boiling  water  until  it  was  at  212^,  he 
transferred  it  to  melting  snow,  and  ascertained 
how  long  it  took  to  fall  a given  number  of  degrees.  Linen 
and  cotton  were  found  to  be  better  conductors  than  wool  and 
the  various  furs,  and  hence  the  reason  that  they  are 
ferred  as  articles  of  summer  clothing  ; but  he  also  found 
that  much  depended  on  the  tightness  with  which  the  sub- 
stances were  packed,  for  the  conducting  power  apparently 
rose  when  they  were  closely  compressed.  These  bodies  act, 
therefore,  as  will  hereafter  be  more  distinctly  seen,  not  so 
much  by  their  own  badly-conducting  power,  as  by  calling 
into  action  the  non-conducting  quality  of  atmospheric  air. 

Crystalline  bodies  do  not  always  conduct  equally  in  every 
direction.  If  a plate  cut  from  a rhombohedral  ci^^stal  be 
warmed  from  a point  at  its  centre,  the  surface  having  been 
previously  coated  with  wax,  it  will  be  found  that  the  fusion 
of  the  wax  takes  place  so  as  to  present  an  ellipse,  the  longer 
axis  of  which  is  in  the  direction  of  the  major  crystalline  axis. 


What  is  the  reason  of  this  ? What  is  the  construction 
Davy’s  safety-lamp  ? On  what  method  did  Rumford  proceed  to  determine 
the  inducting  power  of  clothing?  . What  was  the  effect  compression 
Ho^'  are  these  results  connected  with  the  non-conducting  power  ot 


64 


CONDUCTION  OF  LiaUIDS. 


LECTUEE  XIV. 

Conduction. — Conduction  of  Liquids.— Tramference  of 
Heat  hy  Circulation.  — Conduction  of  Gases.  — Con- 
ducting Power  of  Clothing. 

The  conducting  power  of  most  liquids,  such  as  water,  is 
Fig.  49.  very  low ; a thin  stratum  is  sufficient  almost  en- 
tirely  to  cut  off  the  passage  of  heat.  This  may  he 
j(M  shown  hy  an  apparatus  such  as  Fig.  49,  consisting 
of  a jar,  a,  nearly  filled  with  water,  with  an  air 
thermometer  included  in  such  a manner  that  the 
hulb,  h,  is  within  a short  distance  of  the  surface,  a 
depth  of  a quarter  of  an  inch  or  less  intervening. 
Y The  tube  of  the  thermometer  may  be  passed  through 
jk  the  lower  mouth  of  the  jar,  c,  water-tight  by  means 
of  a cork,  and  the  position  at  which  the  index-liquid 
stands  having  been  marked,  some  ether  is  poured  on  the  sur- 
face of  the  water,  upon  which  it  readily  floats,  and  then  set 
on  fire.  A very  voluminous  flame  is  the  result,  and  a great 
deal  of  heat  is  evolved ; and,  since  the  bulb  of  the  thermom- 
eter is  apparently  separated  from  the  burning  ether  by  a 
thin  film  of  water  only,  if  the  heat  traversed  that  film  the 
thermometer  should  rapidly  move  ; but  the  experiment 
proves  it  does  not ; and  we  therefore  conclude  that  water  is 
a very  bad  conductor  of  caloric. 

While  this  conclusion  is  true,  a little  consideration  will 
show  that  this  experiment  presents  the  facts  in  a very  de- 
ceptive way  ; and  though,  from  its  imposing  character,  it  is 
generally  relied  on  as  a complete  proof,  yet,  were  water  a 
much  better  conductor  than  what  it  actually  is,  the  same 
results  would  be  obtained.  All  flames,  as  we  shall  here- 
after see,  are  hollow  ; they  are  merely  incandescent  on  the 
surface.  A great  distance,  in  reality,  intervenes  between 
the  thermometer  bulb  and  the  points  of  high  temperature, 
and,  in  addition,  the  ether  is  rapidly  evaporating  away  to 
feed  the  flame,  and  all  evaporations  are  cooling  processes. 
To  a certain  extent,  all  liquids  conduct  heat : thus,  mer- 

How  does  the  conducting  power  of  liquids  compare  with  that  of  solids  ? 
How  may  water  be  proved  to  be  a bad  conductor?  What  deceptive  cir- 
cumstances are  there  in  this  experiment  ? Do  liquids  conduct  heat  at  all  ? 


CURRENT  ACTION  IN  WATER. 


65 


cury  is  a very  good  conductor  ; but  in  those  liquids  of  which 
water  is  the  type,  the  dissemination  of  heat  is  chiefly  de- 
termined by  the  mobility  of  their  particles,  a process  which 
passes  under  the  name  of  convection  or  circulation. 

The  apparatus.  Fig.  50,  illustrates  the  nature  of  this  pro- 
cess : it  consists  of  a wide  tube  into  which 
water  may  be  poured ; the  lower  portion,  as 
high  as  a,  being  colored  blue  by  the  addition 
of  some  coloring  substance,  the  intermediate 
portion,  from  a to  b,  being  colorless,  and  the 
upper  portion,  from  b to  c,  being  tinged  yellow. 

Now,  by  the  application  of  a red-hot  iron  ring, 
dy  of  such  a diameter  that  it  can  surround  the 
jar,  a space  of  an  inch  or  more  intervening  all 
rounds  the  upper,  yellow  portion  may  be  made 
even  to  boil : it  shows  no  disposition  to  inter- 
mix with  the  portions  beneath.  But  if  the 
red-hot  ring  is  lowered  down  so  as  to  surround 
the  blue  portion,  as  it  becomes  warm  it  will  be  found  to  as- 
cend, first  through  the  colorless  stratum,  and  finally  through 
that  tinged  yellow,  on  the  top.  When  the  lower  portion  of ' 
a liquid  is  warmed,  currents  are  established,  which,  rising 
through  the  strata  above,  bring  about  a rapid  dissemination 
of  the  heat. 

This  may  also  be  shown  by  taking  a jar.  Fig.  51,  a,  and 
filling  it  with  water,  rendered  a little  more  dense  pig,  51. 
by  some  sulphate  of  soda,  so  as  to  bring  its  speci- 
fic gravity  near  that  of  some  pieces  of  amber 
thrown  into  it.  If  a lamp  now  be  applied  to  the 
bottom  of  the  jar,  currents  are  established  in  the 
water,  rising  up  the  center  and  descending  down 
the  sides  of  the  liquid  ; and  in  this  manner,  new 
portions'  constantly  presenting  themselves  on  the 
surface  exposed  to  the  flame,  the  whole  mass  be- 
comes uniformly  hot. 

The  cause  of  this  movement  is  due  to  the  fact  that  when 
water  is  heated  it  expands.  Those  portions,  therefore,  which 
rest  on  the  bottom  of  the  vessel,  and  to  which  the  heat  is 
applied,  as  soon  as  they  become  warm,  dilate,  and,  being 


What  are  the  relations  of  mercury  in  this  respect  ? By  what  process  does 
the  dissemination  of  heat  in  a liquid  take  place  ? Describe  the  experiment 
represented  in  I<\g.  50.  Describe  that  represented  by  Fig.  51.  What  is 
the  true  cause  of  these  circulatory  movements  ? 


66 


PROPAGATION  OF  HEAT  IN  LIOUIDS. 


Fig.  52. 


lighter  than  before,  rise  to  the  top  of  the  liquid,  while  colder, 
and  therefore  heavier  ones,  occupy  their  place. 

If  we  take  a jar  of  water.  Fig.  52,  and  hav- 
ing introduced  through  apertures  near  the  top  and 
the  bottom  the  thermometers  a b,  and  into  a brass 
trough,  c,  which  surrounds  the  middle  of  the  jar 
Avater-tight,  pour  boiling  water,  after  a little  time 
has  elapsed  we  shall  find  that  the  upper  ther- 
mometer has  risen,  but  the  lower  one  remains 
perfectly  stationary.  The  cause  is,  that  through 
all  those  portions  which  are  above  the  place  at  which  the 
heat  is  applied,  that  is,  the  middle  of  the  vessel,  currents 
are  made  to  circulate,  but  in  all  those  beneath  no  currents 
are  established. 

When,  therefore,  heat  is  applied  to  the  surface  of  water, 
it  is  not  propagated  downward ; when  it  is  applied  to  the 
middle  of  a vessel  containing  that  liquid,  all  the  portions 
above  become  hot,  but  all  those  below  remain  cold ; and 
when  it  is  applied  to  the  bottom  of  the  vessefi  the  whole 
mass  soon  becomes  uniformly  warm. 

In  the  vegetable  world,  advantage  is  taken  of  the  non- 
conducting power  of  water  in  a very  beautiful  Avay.  Soon 
after  sunset,  the  leaves  and  other  delicate  parts  of  plants 
become  covered  with  little  drops  of  dew,  which  invest  them 
on  all  sides.  Under  these  circumstances,  the  process  of  con- 
vection, or  the  establishment  of  currents,  is  entirely  cut  off, 
for  each  of  the  drops  is  isolated,  or  has  no  communication 
with  those  around.  The  cold  air  does  not  so  suddenly  afiect 
these  delicate  organs  as  it  would  do  were  not  this  thin  non- 
conducting film  spread  over  them ; their  action  is,  therefore, 
less  liable  to  be  deranged. 

Recent  accurate  experiments  show  that  all  liquids  con- 
duct to  a certain  extent,  though  in  many  instances  to  a far 
less  extent  than  what  we  see  in  the  case  of  solid  bodies. 
Among  different  liquids,  difference  in  conducting  power  has 
also  been  discovered. 

If  the  conducting  power  of  liquids  is  small,  that  of  gas- 
eous bodies  is  still  less  perceptible.  In  these,  as  in  liquids, 
the  mobility  of  the  particles  is  so  great  that  heat  is  readily 

How  can  it  be  proved  that  the  warm  water  floats  on  the  surface  of  that 
which  is  cold  ? What  is  the  effect  of  applying  heat  to  the  top,  to  the  mid- 
dle, and  to  the  bottom  of  a vessel  containing  water?  What  advantage  is 
taken  in  the  vegetable  world  of  the  non-conducting  power  of  water  ? Do 
all  liquids  conduct  heat  ? Are  there  differences  in  iheir  conducting  power  ? 


PROPAGATION  OF  HEAT  IN  GASES. 


67 


diffused  through  them.  Thus,  if  we  take  ajar, 

Fig.  53,  containing  oxygen  gas,  and  place  a 
piece  of  burning  sulphur  in  it  on  a stand,  a,  the 
vapor  which  rises  from  the  sulphur  moves  in  a 
current  to  the  top  of  the  jar,  and  then  descends 
in  beautiful  wreaths  of  smoke  down  the  sides, 
precisely  representing  the  circulatory  movements 
of  liquids. 

The  ventilation  of  buildings  and  mines,  and 
the  proper  construction  of  furnaces  and  chimneys,  depend 
upon  these  principles. 

By  taking  advantage  of  the  non-conducting  power  of  air, 
rooms  may  be  kept  warm  with  a small  consumption  of  fuel, 
by  furnishing  them  with  double  windows.  A stratum  of 
air,  two  or  three  inches  thick,  intervening  between  the  win- 
dows, effectually  cuts  off  the  passage  of  heat.  It  is  upon 
the  same  principle  we  explain  Count  Rumford’s  experiments 
in  relation  to  the  conducting  power  of  clothing  ; he  found 
111  at  when  the  same  fibres  are  used,  the  apparent  facility 
A\'ith  which  they  transmit  heat  depends  on  the  closeness 
with  which  they  are  packed  : the  non-conducting  power  of 
ail-  is  here  evidently  called  into  play,  and  the  fibres  act  by 
}!reveriting  the  production  of  currents.  In  the  case  of  sheep 
or  other  animals,  which  during  the  winter  season  are  cov- 
ered with  a thick  coat  of  wool  or  fur,  it  is  the  non-conduct- 
ing power  of  the  included  air  which  is  again  brought  into 
operation. 


LECTURE  XV. 

Radiation. — Fr diminary  Ideas  on  Fadiant  Heat. — 
Analogies  with  Light. — Effect  of  Surfaces. — Felations 
between  Radiation  and  Reflection. — The  Florentine  Ex- 
periment.— The  Cold-ray  Experiment. — Opacity  of 
Glass  to  Heat. — Its  increasing  Transparency  as  the 
Temperature  rises. — Properties  of  Rock  Salt. 

But,  though  gases  are  bad  conductors  of  heat,  they  free- 

By  what  process  is  heat  diffused  through  gases?  What  is  the  use  of 
double  windows?  Wliat  connection  has  the  non-conducting  power  of  air 
with  Count  Rumford’s  experiments  ? In  tjie  economy  of  animals,  what  ad- 
vantage is  taken  of  these  principles  ? 


68 


NATURE  OF  RADIANT  HEAT. 


ly  allow  of  its  transmission  by  radiation.  A person  who 
stands  at  one  side  of  a fire  receives  the  heat  of  it,  although 
no  currents  of  warm  air  can  reach  him.  In  a vacuum,  a 
piece  of  red-hot  metal  rapidly  cools. 

The  heat  which,  under  these  circumstances,  escapes  from 
bodies  is  entirely  invisible  to  the  eye ; it  moves  in  straight 
lines,  exhibiting  many  of  the  phenomena  of  the  rays  of  light. 
Thus,  if  we  interpose  between  a fire  and  a thermometer  an 
opaque  screen,  the  moment  the  rays  of  lighkare  stopped  the 
heat  is  simultaneously  intercepted. 

The  rays  of  heat,  like  the  rays  of  light,  are  capable  of 
being  reflected  by  polished  metallic  surfaces.  If  a piece  of 
planished  tin  be  held  before  a fire  in  such  a position  as  to 
reflect  the  light  of  it  upon  the  face,  the  heat,  also,  is  simi- 
larly reflected,  and  gives  rise  to  a sensation  of  warmth. 

The  analogy  between  light  and  heat  is  farther  observed 
when  rays  of  the  latter  fall  upon  bodies  of  a different  phys- 
ical constitution  from  the  metals.  As  glass  is  transparent 
to  light,  there  are  many  bodies  transparent  to  rays  of  heat, 
though,  as  we  are  presently  to  find,  these  bodies  are  not  the 
same  in  both  instances.  And  as  there  are  substances,  like 
lamp-black,  which  will  absorb  all  the  light  which  impinges 
on  them,  there  are  many  which  perfectly  absorb  heat : re- 
flection, transmission,  and  absorption  are  therefore  common 
to  both  these  agents. 

If  we  take  two  metallic  vessels  of  the  same  size  and  shape, 
and  having  blackened  one  of  them  all  over  with  the  smoke 
of  a candle,  fill  them  both  with  hot  water,  and  notice  their 
rate  of  cooling,  it  will  be  seen  that  the  blackened  one  cools 
Fi^.  54.  faster ; the  same  thing  may 

be  observed  if,  instead  of 
blackening  the  vessel,  it  is 
covered  with  layers  of  var- 
nish. These  results  may  be 
proved  by  the  aid  of  Leslie’s 
canister,  which  consists  of 
a cubical  brass  vessel, 
Fig.  54,  set  upon  a verti- 
cal stem,  upon  which  it  can  rotate  j at  a little  distance  is 

Do  gases  tjansmit  radiant  heat  ? How  may  it  be  proved  that  radiant  heat 
moves  in  straight  lines  ? Is  it  capable  of  reflection  ? Are  there  any  sub- 
stances transparent  to  radiant  heat  ? Are  these  the  same  bodies  that  are 
transparent  to  light  ? Of  two  surfaces,  one  polished  and  the  other  blacken- 
ed, which  radiates  heat  best  ? 


VARIATION  OF  SURFACE  RADIAIION. 


69 


placed  the  blackened  bulb  of  a differential  thermometer,  d; 
a mirror,  ili",  receives  the  rays  of  the  canister  and  reflects 
them  on  the  thermometer.  One  of  the  vertical  sides  of  the 
cube  is  left  with  a clear  metallic  surface,  a second  washed 
over  with  one  coat  of  varnish,  the  third  with  two,  and  the 
fourth  with  three  coats ; if  these  sides  be  presented  in  suc- 
cession to  the  thermometer,  they  will  be  found  to  radiate 
heat  with  very  different  degrees  of  speed,  more  heat  escap- 
ing from  them  as  the  number  of  coats  is  increased.  In  the 
experiments  of  Melloni,  it  was  found  that  the  maximum  was 
not  attained  until  sixteen  coats  were  applied. 

These  results  can  only  be  explained  on  the  principle  that 
radiation  does  not  take  place  from  the  surface  of  bodies 
merely,  but  from  a certain  depth  in  their  interior. 

A highly-polished  metal  is  a bad  radiator,  but  on  roughen- 
ing the  surface,  its  quality  is  improved.  As  a general  rule, 
good  radiators  are  bad  reflectors,  and  good  reflectors  are  bad 
radiators. 

When  rays  of  light,  diverging  from  the  focus  of  a concave 
parabolic  mirror,  impinge  on  the  surface,  they  are  reflected 
in  parallel  lines  ; when  parallel  rays  fall  on  such  a surface, 
they  are  reflected  to  its  focus.  Thus,  if  from  the  point,  a, 
Fig,  55,  the  focus  of  a parabolic  concave,  cf,  rays  diverge, 
they  will  be  reflected  in  parallel  lines,  c d /i,  e i,  f k,  and 
if  at  these  points  they  be  intercepted  by  the  mirror,  g k^ 
they  will  be  reflected  to  its  focus,  b. 

Now,  as  the  laws  of  reflection  of  radiant  heat  are  the  same 
as  the  laws  of  the  reflection  of  light,  it  is  plain  that  if  we 
place  any  incandescent  body,  such  as  a red-hot  cannon-ball, 
in  the  focus,  a,  the  heat  which  radiates  from  it  will  finally 
be  found  at  the  other  focus,  b. 

This  is  beautifully  illustrated  by  an  experiment  known 
under  the  name  of  the  experiment  with  conjugate  mirrors. 
In  the  focus,  a.  Fig.  55,  of  a parabolic  mirror,  c /*,  place  a 
red-hot  cannon-ball,  and  in  the  focus,  5,  of  a second  mirror, 
g /c,  set  opposite,  but  twenty  or  thirty  feet  off,  place  a piece 


When  successive  layers  of  varnish  are  put  on  a surface,  what  is  their  ef- 
fect ? When  is  the  maximum  reached  ? What  is  the  explanation  of  these 
results  ? What  is  the  general  connection  between  radiation  and  reflection  ? 
When  rays  diverge  from  the  focus  of  a concave  mirror,  what  is  their  path 
after  reflection  ? When  parallel  fays  fall  on  a concave  mirror,  what  is  their 
path  after  reflection  ? When  a hot  ball  is  placed  in  the  focus  of  one  of  the 
mirrors,  to  what  point  does  its  heat  epnverge  ? Describe  the  Florentine  ex- 
periment represented  in  Fig.  55. 


70  OPACITY  OF  GLASS  TO  HEAT. 

of  phosphorus,  a screen  intervening  between.  As  soon  as 
the  arrangements  are  completed,  remove  the  screen,  and  in 
Fig.  55. 


j 


a moment  the  phosphorus  takes  fire.  That  this  effect  is  due 
to  the  reflecting  action  of  the  mirrors,  as  has  been  described, 
may  be  proved  by  removing  the  mirror,  cf^  when  it  will  be 
found  that  the  phosphorus  can  not  be  lighted,  even  though 
the  ball  be  brought  within  a very  short  distance  of  it. 

This  striking  experiment  proves,  first,  that  the  rays  of 
heat  move  in  straight  lines,  like  those  of  light ; and,  second, 
that  in  the  same  manner  they  are  subject  to  the  ordinary 
laws  of  reflection. 

A variation  of  the  foregoing  experiment  may  be  made  by 
using  a snowball  instead  of  the  cannon-shot,  in  which  case 
a thermometer  placed  in  the  focus  of  the  opposite  mirror 
will  exhibit  a reduction  of  temperature.  From  this  it  was 
at  one  time  supposed  that  there  existed  rays  of  cold  precisely 
analogous  to  rays  of  heat,  and  that  they  observed  the  same 
law  as  respects  the  rectilinear  nature  of  their  movement, 
and  were  also  subject  to  the  law  of  reflection ; but,  as  we 
shall  see  when  we  come  to  speak  of  the  Theory  of  the  Ex- 
changes of  Heat,  a simple  explanation  of  the  whole  result 
can  be  given,  without  implying  the  existence  of  a principle 
of  cold  analogous  to  the  principle  of  heat. 

Let  it  be  now  supposed  that  in  the  focus  of  the  mirror, 
g k,  Fig.  55,  the  bulb  of  a delicate  thermometer  is  placed, 
and  in  the  focus  of  the  other  mirror,  cf,  a,  metalline  mass,  a, 

What  two  facts  does  this  experiment  prove  ? When  a snowball  is  used 
instead  of  a hot  shot,  what  is  the  result  ? 


RADIANT  HEAT  OF  DIFFERENT  COLORS. 


71 


v.he  temperature  of  which  we  can  vary  at  pleasure.  Be- 
tween the  mirrors  let  there  be  interposed  a screen  of  trans- 
parent plate  glass  ; and  let  us  farther  suppose  that  the  tem- 
perature of  a is  212°,  or  considerably  below  the  point  at 
which  it  is  visibly  red  hot.  Under  these  circumstances  the 
thermometer  exhibits  no  rise  of  temperature  so  long  as  the 
glass  intervenes,  but  the  moment  it  is  removed  the  heat 
passes. 

A piece  of  transparent  glass  is  therefore  opaque  to  the 
rays  of  heat  which  come  from  a non-luminous  source. 

Let  us  now  suppose  that  the  temperature  of  the  metalline 
mass,  a,  continually  rises.  When  it  has  reached  a red  heat, 
a certain  proportion  of  the  rays  emitted  by  it  begins  to  pass 
through  the  glass,  as  is  shown  by  their  effect  upon  the  ther- 
mometer. When  the  mass  is  visibly  red  hot  in  the  daylight, 
the  rays  go  through  the  glass  more  readily,  and  when  it  has 
become  white  hot,  or  has  reached  the  highest  temperature 
we  can  give  it,  the  glass  transmits  the  rays  with  facility. 

These  facts  are  of  the  utmost  importance.  They  show 
that  bodies  transparent  to  light  are  not  necessarily  trans- 
parent to  heat,  and,  therefore,  that  light  and  heat  are  sep- 
arate and  independent  agents.  They  farther  show  that,  as 
respects  glass,  its  transparency  for  heat  differs  with  the  tem- 
perature of  the  source  from  which  the  rays  come. 

There  is  a certain  well-known  substance,  rock  salt,  with 
which,  if  we  could  obtain  plates  large  enough  to  intervene 
completely  between  the  two  mirrors,  a different  series  of  re- 
sults would  be  exhibited.  Whatever  might  be  the  tempera- 
ture of  the  source,  whether  low  or  high,  the  rays  would  pass 
it  with  equal  freedom.  The  warmth  of  the  hand  and  the 
rays  from  melting  iron  would  go  through  it  alike.  This 
substance,  therefore,  is  permeable  to  all  kinds  of  heat,  as 
glass  is  permeable  to  all  kinds  of  light.  It  constitutes  the 
true  glass  for  heat. 

The  great  conclusion  which  we  draw  from  the  experi- 
ments just  described  is,  that  there  are  different  varieties 
of  radiant  heat.  Some  of  them  can  pass  through  glass, 
and  some  can  not.  Hereafter  we  shall  see  that  the  intrin- 

Whal  is  the  relation  of  glass  to  radiant  heat  of  low  intensity?  What 
changes  take  place  in  the  transmissive  power  of  the  glass  as  the  temper- 
ature rises  ? How  are  these  facts  connected  with  the  physical  independ- 
ence of  light  and  heat  ? What  are  the  properties  of  rock  salt  ? Why  is  it 
the  glass  of  heat?  What  general  conclusion  is  drawn  from  the  foregoing 
facts  ? 


72 


THEORY  OF  EXCHANGES  OF  HEAT. 


sic  differences  in  radiant  heat  are  due  to  the  same  cause 
which  gives  different  colors  to  light. 


LECTURE  XVI. 

Theory  of  the  Exchanges  of  Heat.  — Physical  Inde- 
pendence of  Light  and  Heat. — Theory  of  Exchanges. 
— Explanation  of  the  Cold  Ray  Experiment. — Well^ s 
Theory  of  the  Deiv. — Cold  on  Mountain  Tops. — Con- 
duction a Form  of  Radiation.  — Temperature  of  the 
Sun. 

The  earlier  writers  on  chemistry  supposed  that  if  light 
and  heat  are  not  the  same  principle,  they  are  mutually  con- 
vertible ; that  when  the  rays  of  light  fall  on  any  object  and 
warm  it,  they  do  so  because  they  become  extinguished  and 
changed  into  heat. 

But  there  are  many  facts  which  militate  against  this  doc- 
trine. A vessel  containing  hot  water  radiates  heat,  and  that 
heat  is  totally  invisible  in  a dark  room,  nor  can  it  be  made 
to  assume  the  luminous  condition,  even  though  concentrated 
by  large  concave  mirrors. 

In  addition,  as  we  have  already  shown,  the  relation  of 
transparency  for  these  two  agents  is  not  the  same.  A piece 
of  smoky  quartz,  or  dark-colored  mica,  of  such  a degree  of 
opacity  as  scarcely  to  admit  a ray  of  light  to  pass,  is  freely 
traversed  by  radiant  heat. 

Theory  of  the  Exchanges  of  Heat. 

The  theory  of  the  exchanges  of  heat,  comprehending  an 
explanation  of  a great  number  of  the  phenomena  we  ordina- 
rily witness,  depends  upon  the  following  principles : It  as- 
sumes, 1st,  that  all  bodies,  no  matter  what  their  temperature 
may  be,  are  constantly  radiating  heat  at  all  times  ; 2d. 
That  the  rate  of  radiation  depends  on  the  temperature,  in- 
creasing as  the  temperature  rises,  and  diminishing  as  it  de- 
clines. 

What  are  the  varieties  of  radiant  heat  due  to  ? What  relation  was  for- 
merly supposed  to  exist  between  light  and  heat  ? Can  rays  of  heat  exist 
without  being  visible?  Can  light  exist  unaccompanied  by  heat?  What 
other  evidence  have  we  of  the  p%sical  independence  of  these  agents  ? On 
what  does  the  theory  of  the  exchanges  of  heat  depend  ? 


THEORY  OF  EXCHANGES  OF  HEAT. 


73 


Thus  the  various  objects  around  us  are  constantly  emit- 
ting caloric,  the  warm  bodies  to  the  cold,  and  the  cold  ones 
to  the  warm.  A mass  of  snow  and  a red-hot  cannon-ball 
respectively  give  off  heat,  the  ball  emitting  it  in  great  quan- 
tities, and  the  snow  in  less.  And  even  when  adjacent  bod- 
ies have  reached  the  same  thermometric  point,  they  still  con- 
tinue to  exchange  heat  with  one  another. 

Upon  these  principles,  we  can  readily  account  for  the  fact 
that  bodies  of  different  temperatures  at  first,  finally  come 
to  an  equilibrium.  If  an  ignited  cannon-shot  be  placed  in 
the  middle  of  a large  room,  it  radiates  its  heat  to  the  ceiling, 
the  walls,  the  floor,  and  the  various  objects  around ; they 
also  radiate  back  again  upon  it ; but,  from  its  elevated  tem- 
perature, it  emits  its  heat  faster  than  they,  and  therefore 
gives  out  more  than  it  receives.  Its  temperature  constantly 
descends,  and  continues  to  do  so  until  it  receives  just  as 
much  as  it  gives,  which  takes  place  when  it  has  reached  the 
same  degree  as  the  objects  around ; for,  other  things  being 
equal,  bodies  at  the  same  temperature  radiate  with  equal 
speed. 

The  process  must,  however,  stop  as  soon  as  that  equality 
of  temperature  is  attained  ; for,  if  we  suppose  the  shot  to 
cool  below  that  point,  it  would  evidently  begin  to  receive 
more  heat  from  the  objects  around  than  it  gave  forth,  and 
the  excess  accumulating  in  it,  its  temperature  would  at  once 
rise. 

"When  an  equilibrium  is  obtained  the  process  of  radiation 
still  continues,  but  the  exchanges  are  equal.  Two  lighted 
candles  placed  together  do  not  extinguish  each  other,  or 
cease  to  exchange  light  with  each  other,  nor  do  two  bodies 
equally  warm  cease,  for  that  reason,  to  exchange  heat  In 
a room,  therefore,  in  which  every  thing  has  the  same  tem- 
perature, rays  are  continually  exchanging,  but  each  object 
maintains  its  own  temperature,  because  it  receives  as  much 
as  it  gives. 

If  a red-hot  ball  and  a thermometer  bulb  are  placed  near 
one  another,  the  bulb  receives  more  heat  from  the  ball  than 
it  gives  to  it,  and  its  temperature  therefore  rises  ; but  if  a 
thermometer  bulb  and  a snow-ball  are  placed  in  presence 


Do  bodies  at  the  same  temperature  still  radiate  ? Describe  the  process 
of  cooling  of  an  incandescent  body.  When  does  the  descent  of  temperature 
cease  ? When  an  equilibrium  is  obtained,  what  is  the  rate  of  exchanges  ? 
Describe  the  action  in  the  case  of  a red-hot  ball  and  a thermometer  bulb. 

D 


74 


THEORY  OF  THE  DEW* 


of  one  another,  the  bulb,  being  the  hotter  body,  gives  mora 
than  it  receives,  and  its  temperature  therefore  descends. 
This  is  the  explanation  of  the  experiment  'with  the  conju- 
gate mirrors.  That  experiment,  as  was  observed,  affords  no 
proof  that  there  are  rays  of  cold  : the  effect  is  due  to  the 
fact  that  a mutual  exchange  is  going  forward  between  the 
two  bodies,  and  the  temperature  of  the  hotter  descends.  The 
mirrors,  of  course,  take  no  part  in  this  phenomenon ; their 
office  is  merely  to  direct  the  path  of  the  rays,  as  has  been 
explained. 

Gn  the  principles  of  the  radiation  of  heat  is  founded  Wells’s 
theory  of  the  dew.  After  the  sun  goes  down  of  an  evening, 
drops  of  water  condense  on  the  leaves,  grass,  stones,  and 
other  objects  exposed  to  the  air.  It  was  once  a question 
whether  this  dew  descended  in  the  form  of  a light  shower, 
or  ascended  from  the  ground.  There  are  also  certain  cir- 
cumstances apparently  very  mysterious  attending  its  forma- 
tion : the  dew  rarely  falls  on  a cloudy  night ; it  also  appa- 
rently possesses  a selecting  power,  depositing  itself  on  some 
bodies  in  preference  to  others.  The  theory  of  Dr.  Wells  fur- 
nishes a beautiful  explanation  of  these  curious  facts.  During 
the  day,  the  various  bodies  on  the  surface  of  the  earth,  re- 
ceiving the  rays  of  the  sun,  become  warm ; but  at  nightfall, 
when  the  sky  is  unclouded,  they  begin  to  cool ; for,  the  pro- 
cess of  radiation  continuing  without  any  source  of  supply, 
their  temperature  must  descend.  While  the  sun  shone  they 
received  as  much  heat  from  him  as  they  gave  forth  to  the 
^%y,  but  when  he  sets  the  supply  is  cut  off,  and  they  there- 
4>re  cool ; and  as  there  is  always  moisture  in  the  air,  their 
=«mperature  descending,  by-and-by  the  dew  point  is  reach- 
tJd  ; they  become  cold  enough  to  condense  water  from  the 
surrounding  air,  and  this  is  the  dew.  And  as  different  bod 
ies,  according  to  the  roughness  or  physical  condition  of  theii 
surfaces,  radiate  with  different  degrees  of  speed,  as  Leslie’s 
canister  proves,  some  of  the  objects  exposed  to  the  sky  cool 
rapidly,  and  are  covered  with  dew ; but  with  others  the  dew 
point  is  never  reached  : hence  the  apparent  selecting  power. 
When  there  is  a canopy  of  clouds  over  the  sky,  dew  can  not 
form,  for  the  cloud  radiates  to  the  earth  as  much  as  the 


Describe  the  action  of  a snow-ball  and  a thermometer  bulb.  How  is  this 
connected  with  the  experiment  with  conjugate  mirrors  ? Unde’*  what  cir- 
cumstances does  dew  form?  What  is  the  theory  of  Wells?  How  aocs 
this  explain  the  selecting  power  of  bodies  ? 


CONDUCTION. 


75 


earth  radiates  to  it : the  exchanges  are  equal,  and  the  equi- 
librium is  maintained  ; but  if  the  cloud  disappears,  the  heat 
of  the  surface  of  the  ground  escapes  away  into  the  regions 
of  space,  and  is  lost ; hence  cloudy  nights  are  warm,  and  a 
clear  is  often  a frosty  night. 

For  similar  reasons,  mountain  tops  are  always  colder  than 
valleys.  In  a valley,  the  radiation  is  obstructed  by  the  sides 
of  the  adjacent  hills,  but  on  the  top  of  a mountain  the  free 
exposure  to  the  sky  permits  of  unchecked  radiation. 

It  has  already  been  observed,  that  conduction  is  only  a 
form  of  radiation.  In  its  ordinary  acceptation,  the  term  con- 
duction implies  passage  from  particle  to  particle,  by  reason 
of  their  being  in  contact ; but  we  have  proved  that  the  con- 
stitution of  matter  involves  the  existence  of  intorstices,  and 
that  heat  can  only  pass  from  among  these  by  radiating  across 
the  interstices  ; hence  the  term  interstitial  radiation. 

An  interesting  conclusion  may  be  drawn  from  the  condi 
tions  of  the  passage  of  radiant  heat  through  glass.  We  have 
seen  it  is  necessary  that  the  heat  should  come  from  a source 
of  very  high  temperature  to  pass  this  medium  with  facility. 
Now  the  heat  of  the  sun  passes  with  the  greatest  freedom, 
as  is  well  known  when  we  stand  before  a window  through 
which  the  sun  shines.  In  the  focus  of  a convex  lens  of 
glass  exposed  in  the  sun’s  rays,  bodies  may  be  readily  set  on 
fire.  We  infer,  therefore,  that  the  temperature  of  the  sun 
is  very  high,  a result  which  is  corroborated  by  proofs  drawn 
from  other  sciences. 


LECTURE  XYII. 

Of  Light. — Sources  of  Light.  — The  Sim. — Incande- 
scence.— Combustion. — Different  Colors  of  Lights. — 
Shadoivs. — Conditions  of  the  Intensity  of  Light. — 
Fhotometers^  Rumford's,  Ritchie's^  and  the  Extinction 
of  Shadows. — Velocity  of  Light. — Law  of  Reflection. 
— Refraction. — Burning  Glasses. 

The  phenomena  of  radiant  heat  lead  us  by  imperceptible 
steps  to  the  phenomena  of  light.  In  treating  of  the  former, 

How  does  it  explain  the  action  of  clouds  ? Why  is  it  colder  on  mount- 
ains than  in  valleys  ? What  is  meant  by  interstitial  radiation  ? What  con 
elusion  may  be  drawn  as  respects  the  temperature  of  the  sun  ? 


70 


NATURE  OF  LIGHT. 


we  have  in  many  cases  drawn  illustrations  from  the  latter ; 
and,  indeed,  there  are  facts  in  relation  to  caloric  which  it 
is  absolutely  impossible  to  understand  until  we  comprehend 
the  analogous  facts  in  light. 

Light  may  be  artificially  produced  by  many  different  pro- 
cesses, such  as  the  ignition  of  solids,  combustion,  and  phos- 
phorescence. Any  solid,  if  sufficiently  heated,  becomes  lu- 
minous j combustible  gases  take  fire  at  a certain  temperature 
in  the  air  ; and  the  diamond  will  emit  a phosphorescent  glow 
in  a dark  place,  after  it  has  been  exposed  to  the  day. 

It  is,  however,  to  the  sun  that  we  are  chiefly  indebted. 
The  quantity  of  light  furnished  by  him  infinitely  exceeds 
that  of  all  other  natural  and  artificial  sources,  and  its  brill- 
iancy is  so  great  that  the  electric  spark  alone  rivals  it. 

When  the  temperature  of  solid  substances  is  raised  to 
1000°  Fahrenheit,  they  begin  to  be  luminous  in  the  day- 
light, or,  as  it  is  termed,  are  visibly  red-hot.  It  requires  a 
far  higher  temperature  to  render  a gas  incandescent.  This 
may  be  shown  by  holding  a piece  of  thin  platina  wire  in  the 
current  of  hot  air  which  rises  from  the  apex  of  the  flame  of 
a lamp  ; the  air  is  not  visibly  ignited,  but  the  platina  wire 
instantly  becomes  red-hot,  showing  the  great  difference  in 
this  respect  between  this  metal  and  a gas. 

Different  vapors  and  gases  evolve  different  quantities  of 
light  when  ignited.  The  flame  of  burning  hydrogen  is 
scarcely  visible  in  the  daylight  j that  of  alcohol  is  but  little 
brighter ; but,  under  the  same  circumstances,  sulphuric  ether 
emits  much  light.  If  we  take  a glass 
of  the  form  Fig.  56,  consisting  of  a 
bulb,  a,  and  curved  tube,  b,  and,  hav- 
ing filled  the  bulb  with  ether,  cause 
it  to  boil  by  the  application  of  a lamp, 
c,  the  ether  may  be  set  on  fire  as  it  is 
forced  out  of  the  vessel  by  the  pressure 
of  its  vapor.  It  burns  in  a beautiful 
arch  of  great  brilliancy ; but  if  we  substitute  alcohol  for 
ether,  the  light  becomes  quite  insignificant. 

The  light  which  is  emitted  by  lamps  and  candles  is,  how- 
ever, in  reality,  due  to  the  disengagement  of  solid  matter. 


Mention  some  of  the  sources  of  light.  At  what  temperature  do  solids  be- 
come incandescent  ? In  the  combustion  of  vapors  and  gases,  is  there  any 
difference  in  the  amount  of  light  emitted  ? How  may  this  be  illustrated  ? 
To  what  cause  are  we  to  attribute  the  light  emitted  by  lamps  and  candles  ? 


ARTIFICIAL  LIGHT. 


77 


The  constituents  of  the  gas  which  produces  the  flame  are 
carbon  and  hydrogen  chiefly ; of  these,  the  latter  is  the 
more  combustible,  and  is  first  burned ; for  a moment,  there- 
fore, the  carbon  exists  in  a solid  form,  in  a state  of  extreme 
subdivision,  and  at  a high  temperature,  but  being  in  con- 
tact with  the  external  air,  it  is  immediately  consumed. 

Artificial  lights  differ  in  color.  If  alcohol  be  mixed  with 
common  salt  and  set  on  fire,  the  flame  is  of  a yellow  tint ; 
if  with  boracic  acid,  it  is  green  ; if  with  nitrate  of  strontian, 
it  is  red.  It  is  upon  these  principles  that  the  art  of  pyro- 
techny  depends. 

From  whatever  source  light  may  come,  it  exhibits  the 
same  physical  properties.  It  moves  in  straight  lines.  When 
it  impinges  on  polished  metallic  surfaces,  it  is  reflected  ; on 
dark  surfaces,  it  is  absorbed ; on  transparent  surfaces,  as 
glass,  it  is  transmitted.  In  the  last  case,  it  is  frequently 
forced  into  a new  path,  as  we  shall  presently  see,  and  then 
the  phenomenon  takes  the  name  of  refraction,  because  the 
ray  is  broken  from  its  primitive  course. 

There  are  two  different  kinds  of  opacity,  black  and  white  ; 
charcoal  is  a black  opaque  substance,  earthen-ware  is  opaque 
white. 

The  shadows  formed  by  opaque  bodies  arise  from  the  in- 
terception of  light  in  its  rectilinear  progress.  They  may  be 
of  two  different  kinds,  the  common  and  geometrical ; the 
former  arises  from  a luminous  surface,  the  latter  from  a lucid 
point ; the  former  consists  of  two  portions,  the  umbra  and 
'penumbra  ; in  the  latter,  the  passage  from  total  darkness  to 
light  on  the  side  of  the  shadow  is  abrupt,  and  without  the 
intervention  of  any  shade. 

The  illuminating  power  of  a light  depends  upon  several 
conditions.  As  the  distance  increases  it  becomes  less,  the 
effect  being  inversely  as  the  square  of  the  distance  ; that  is, 
at  two  feet  it  gives  only  one  fourth  of  what  it  would  do  at 
one,  at  three  feet  only  one  ninth.  The  absolute  intensity 
of  the  light  also  determines  the  result ; thus,  there  are  flames 
that  are  very  brilliant,  and  others  that  are  paler  : the  mag- 
nitude of  the  luminous  surface  is  another  of  these  conditions. 
The  absorbent  effect  exerted  on  the  passing  rays  by  the  air. 

How  may  artificial  yellow,  green,  and  red  lights  be  made  ? In  what 
course  does  light  move  ? What  is  meant  by  the  reflection,  absorption,  trans- 
mission, and  refraction  of  light  ? How  many  kinds  of  opacity  are  there  ? 
What  is  the  difference  between  common  and  geometrical  shadows  ? Whstt 
conditions  determine  the  illuminating  power  of  light  ? 


78 


PHOTOMETRY. 


or  medium  traversed,  another  ; as  is  also  the  direct  or  oblique 
manner  in  which  the  rays  are  received  on  the  illuminated 
surface. 

Of  Photometers  and  the  Measurement  of  Light. 

The  methods  resorted  to  for  the  measurement  of  the  in- 
tensity of  light  are  very  inferior  to  those  for  heat.  They 
are  not  absolute,  but  comparative  measures.  Three  are  in 
common  use  : they  are  known  as  E-umford’s  method,  Ritch- 
ie’s method,  and  the  method  of  extinction  of  shadows. 

Eumford’s  method  depends  on  the  principle  that  of  two 
lights,  the  most  brilliant  will  cast  the  deepest  shadow.  If, 
therefore,  the  lights  to  be  compared  are  made  to  cast  shad- 
ows of  the  same  opaque  body,  side  by  side,  upon  a piece  of 
paper,  the  eye  can,  without  difficulty,  determine  which  of  the 
shadows  is  darkest,  and  the  light  which  casts  it  being  moved 
to  a greater  distance,  or  the  other  being  brought  nearer, 
when  the  two  shadows  are  of  precisely  the  same  depth,  the 
distances  of  the  lights  from  the  paper  will  indicate  their 
relative  illuminating  power ; thus,  if  one  is  twice  as  far  off 
as  the  other,  its  intensity  is  four  times  as  great. 

Ritchie’s  photometer  depends  on  the  equal  illumination 

of  surfaces.  It  con- 
sists of  a box,  a b, 
six  or  eight  inches 
long,  and  one  broad 
and  deep.  Fig.  57, 
in  the  middle  of 
which  a wedge  of 
woodj/'e^,  is  placed, 
with  its  angle,  e,  up- 
ward. This  wedge  is 
covered  with  white 
paper,  neatly  doub- 
led to  a sharp  line  at  e.  In  the  top  of  the  box  there  is  a 
conical  tube,  with  an  aperture,  d,  at  its  upper  end,  to  which 
the  eye  is  applied,  and  the  whole  may  be  raised  to  any  suit- 
able height  by  means  of  the  stand,  c.  On  looking  down 
through  d,  having  previously  placed  the  two  lights,  m n,  the 
intensity  of  which  we  desire  to  determine,  on  opposite  sides 
of  the  box,  they  illuminate  the  paper  surfaces  exposed  to 
them,  and  the  eye  sees  both  those  surfaces  at  once.  By 
Describe  Rumford’s  and  Ritchie’s  photometric  methods. 


mg.  57. 


PHOTOMETRY. 


79 


changing  the  position  of  the  lights,  we  eventually  make  them 
illuminate  the  surfaces  equally,  and  then,  measuring  their 
distances  from  e,  their  illuminating  powers  are  as  the  squares 
of  those  distances. 

In  both  this  and  the  preceding  method,  a difficulty  arises 
when  the  lights  to  be  compared  are  of  different  tints.  To 
some  extent,  this  may  be  avoided  by  placing  in  Ritchie’s  in- 
strument a colored  glass  at  d. 

The  third  method,  that  of  extinction  of  shadows,  is  much 
more  exact,  differences  in  the  color  of  the  lights  even  serv- 
ing to  give  greater  accuracy.  It  depends  on  the  following 
principle.  If  a light  is  made  to  throw  the  shadow  of  an 
opaque  object  upon  a white  screen,  there  is  a certain  distance 
at  which,  if  a second  light  be  brought,  its  rays,  illuminating 
the  screen,  will  totally  obliterate  all  traces  of  the  shadow. 
It  has  been  found  that  eyes  of  average  sensitiveness  fail  to 
distinguish  the  effect  of  a light  when  it  is  in  presence  of  an- 
other sixty- four  times  as  intense.  The  precise  number  varies 
with  different  eyes,  but  to  the  same  eye  it  is  always  the 
same.  If  there  be  any  doubt  as  to  the  perfect  disappear- 
ance of  the  shadow,  the  receiving  screen  may  be  agitated 
or  moved  a little.  This  brings  the  shadow,  to  a certain  ex- 
tent, into  view  again.  Its  place  can  then  be  traced,  and  on 
ceasing  the  motion  the  disappearance  verified. 

When,  therefore,  we  desire  to  measure  the  relative  intens- 
ities of  lights,  we  have  only  to  determine  at  what  distance 
they  will  extinguish  a given  shadow.  Their  intensities  are 
as  the  squares  of  those  distances.  This  is  the  method  by 
which  I determined  the  amount  of  light  given  off  by  ignit- 
ed solids  at  various  temperatures,  as  will  be  hereafter  men- 
tioned. 

Light  does  not  move  from  point  to  point  instantaneously, 
but  at  a rate  which  is  measurable.  From  certain  astro- 
nomical facts,  it  appears  that  the  velocity  is  about  192,000 
miles’ per  second. 

When  a ray  falls  upon  a polished  surface  it  suffers  reflex- 
ion, and  when  it  falls  upon  a transparent  medium  it  under- 
goes refraction. 

It  is  in  consequence  of  this  that  convex  lenses  converge 
the  rays  of  the  sun,  and  so  produce  a high  temperature.  In 

What  difficulty  is  encountered  in  these  methods?  On  what  principle 
does  the  method  by  extinction  of  shadows  depend  ? Describe  the  process. 
At  what  rate  does  light  move  ? 


80 


newton’s  discoveries. 


Fig.  58. 


this  application  they  are  called 
burning  glasses,  and,  until  the 
invention  of  the  Voltaic  pile 
and  oxyhydrogen  blowpipe, 
presented  the  most  energetic 
means  for  elevation  of  temper- 
ature. If  made  of  thin  and 
pure  glass,  and  of  a diameter 
of  from  one  to  three  feet,  these 
lenses  will  effect  the  instan- 
taneous fusion  of  most  earthy 
and  metallic  bodies.  Even 
the  most  fixed  metals  volatil- 
ize at  the  focal  point. 


LECTURE  XYIII. 

The  Constitution  op  Solar  Light. — Newto7i"s  Discov- 
eries.— The  Solar  Spectrum. — Order  of  the  Intensity 
of  Light. — Distribution  of  Heat. — The  Chemical  Ef- 
fects.— Distribution  of  Chemical  Power. — Fixed  Lines. 


Fig.  60. 


Sir  Isaac  Newton  first  succeeded  in  proving 
the  compound  nature  of  light  by  the  aid  of  a very 
simple  instrument,  a glass  prism.  It  consists  of 
a piece  of  glass  having  three  sides.  Fig.  5^,  a a, 
and  is  usually  mounted  on  a brass  stand,  b,  with 
a ball  and  socket  joint,  c,  which  allows  us  to 
place  it  in  any  required  position. 

Let  the  shutters  of  a room  be  closed,  and 
through  an  aperture  in  one  of  them, 
suitably  situated,  let  a beam  of  the  sun 
enter,  Fig.  60,  a.  It  pursues,  of  course, 
a straight  path,  following  the  dotted 
^ line,  a e.  Now  let  the  prism  interpose 
in  the  position,  b c,  so  as  to  intercept 
completely  the  ray.  This  goes  no  longer 
to  e,  but  is  bent  out  of  its  course,  and 
moves  in  the  direction  d. 

Two  striking  facts  are  now  to  be  re- 


What  are  burning  glasses  ? Describe  the  prism.  State  the  effect  which 
ensues  when  a ray  passes  through  the  prism. 


THE  SOLAR  SPECTRUM. 


81 


marked : first,  the  ray  a is  refracted  or  broken  from  its  path ; 
and,  second,  instead  of  forming  on  the  surface  d,  upon  which 
it  falls,  a white  spot,  an  elongated  and  beautifully-colored 
image  is  produced.  These  colors  are  seven  in  number : red, 
orange,  yellow,  green,  blue,  indigo,  violet.  The  separation 
of  these  colors  from  one  another  is  designated  by  the  term 
Dispersion. 

Newton  has  shown  that  white  light  consists  of  these  vari- 
ous-colored rays  blended  together ; and  their  separation  in 
the  case  before  us  is  due  to  the  fact  that  the  prism  refracts 
them  unequally.  On  examining  the  position  of  the  colors, 
in  their  relation  to  the  point  e,  to  which  they  would  all  have 
gone  had  not  the  prism  intervened,  it  is  ascertained  that  the 
red  is  least  disturbed  or  refracted  from  its  original  path,  and 
the  violet  most ; for  these  reasons,  we  call  the  red  the  least 
refrangible  ray,  the  violet  the  most  refrangible,  and  the  yel- 
low intermediately. 

That  the  mixture  of  these  colored  rays  reproduces  white 
light,  may  be  proved  by  resorting  to  any  optical  contrivance 
which  will  reassemble  them  all  in  one  point ; that  point 
will  be  perfectly  white. 

Let  V r.  Fig,  61,  represent  the  spectrum  which  is  given 
by  a sunbeam  after  its  passage  through  a prism,  and  e the 
point  to  which  it  would  have  gone  had  not  the  prism  inter- 
vened ; the  order  of  the  colors  commencing  with 
that  which  is  least  disturbed  from  its  path,  or  near- 
est to  e,  is  as  follows  : 

Red, 

Orange, 

Yellow, 

Green, 

Blue, 

Indigo, 

Violet. 

These  colors  gradually  blend  into  each  other,  so 
that  their  boundaries  can  not  be  traced ; and  in- 
stead of  a circular  spot,  which  would  have  resulted 
had  they  gone  forward  to  e,  they  are  dilated  out,  so  as  to 
form  an  elongated  figure  with  parallel  sides  ; at  the  two  ex- 
tremities the  light  fades  gradually  away,  so  that  we  can  not 
trace  its  limit  with  precision. 

What  is  meant  by  refraction  ? What  by  dispersion  ? What  is  Newton’s 
theory  of  the  constitution  of  light  ? Which  is  the  least,  and  which  the  most 
refrangible  ray  ? Of  what  does  white  light  consist  ? What  is  the  order  of 
refrangibility  of  colors  ? What  is  the  figure  of  the  spectrum  ? 

D 2 


Fig.  61. 


82  DISTRIBUTION  OP  HEAT  IN  THE  SPECTRUM. 


Besides  this  difference  of  color,  the  light  differs  in  intrin= 
sic  brilliancy  in  the  different  spaces.  Thus,  if  we  receive 
the  spectrum  on  a piece  of  finely-printed  paper,  we  can  read 
the  letters  in  each  color  at  very  different  distances.  In  the 
yellow  region  the  light  is  most  brilliant,  and  there  we  can 
read  farthest.  From  this  point  the  light  declines  in  brill- 
iancy to  the  two  ends  of  the  spectrum,  its  intensity  in  the 
colored  spaces  being  in  the  following  order  : 

Yellow, 

Green, 

Orange, 

Red, 

Blue, 

Indigo, 

Violet. 


Sir  W.  Herschel  discovered,  while  using  large  reflecting 
telescopes,  that  the  calorific  rays  of  the  sun  pass  with  differ- 
ent degrees  of  facility  through  colored  glasses,  and  was  led 
to  examine  the  temperature  of  the  colored  spaces  of  the  so- 
lar spectrum,  to  see  whether  the  intensity  of  the  heat  follows 
the  intensity  of  the  light.  It  was  reasonable  to  suppose  that 
the  yellow  space,  being  the  brightest,  would  be  also  the  hot- 
test. He  therefore  placed  delicate  thermometers  in 
the  various  colored  spaces,  and  kept  them  in  these 
spaces  until  they  had  risen  as  high  as  the  ray  could 
bring  them.  The  thermometer  v,  Fig,  62,  had 
risen  the  least,  and  in  succession,  z,  y,  o,  r;  that 
which  was  immersed  in  the  red  being  the  highest,. 

It  thus  appears  that  the  distribution  of  heat  in 
the  colored  spaces  of  the  solar  spectrum  is  not  the 
same  as  the  distribution  of  light ; that  the  yellow 
ray,  though  it  is  the  most  luminous,  is  far  from  being 
the  hottest,  and  that  the  intensity  of  the  heat  stead- 
ily increases  from  the  violet  to  the  red  extremity. 

But  this  is  not  all : he  farther  found,  that  if  a thermom- 
eter be  brought  out  of  the  red  region  in  the  position  x,  be- 
yond the  limits  of  the  spectrum,  and  where  there  is  no  light 
whatever,  it  stands  higher  than  any  of  the  others.  From 
this  a most  important  conclusion  may  be  drawn,  that  the 
light  and  heat  existing  in  the  sunbeam  are  distinct  and  in- 


How  may  the  illuminating  power  be  determined  ? What  is  the  order  of 
illuminating  power?  Describe  the  discovery  of  Sir  W.  Herschel.  Is  the 
distribution  of  heat  in  the  spectrum  the  same  as  the  distribution  of  light  ? 
What  fact  indicates  that  the  light  and  heat  are  separate  and  independent 
agents  ? 


RAYS  OP  CHEMICAL  ACTION. 


83 


dependent  agents,  and  that  such  processes  as  we  are  con- 
sidering they  may  he  perfectly  separated  from  each  other. 

It  was  discovered  by  some  of  the  alchemists,  centuries 
ago,  that  the  chloride  of  silver,  a substance  of  snowy  white 
ness,  turns  black  on  exposure  to  the  light.  More  recently, 
a great  number  of  such  bodies  have  been  found — bodies 
which  change,  with  greater  or  less  rapidity,  under  the  influx* 
ence  of  this  agent.  The  iodide  of  silver,  which  forms  the 
basis  of  the  process  known  as  the  Daguerreotype,  is  such  ; 
and  a mixture  of  chlorine  and  hydrogen  gases  in  equal  vol- 
umes, though  it  may  be  kept  unchanged  for  a great  length 
of  time  in  the  dark,  explodes  violently  on  exposure  to  the 
sunshine.  In  the  same  manner,  changes  take  place  in  a 
great  variety  of  organic  compounds  ; the  most  delicate  veg- 
etable hues  are  soon  bleached,  and,  indeed,  a ray  of  light  can* 
scarcely  fall  on  a surface  of  any  kind  without  leaving  traces 
of  its  action. 

If  a piece  of  paper,  spread  over  with  chloride  of  silver,  be 
placed  in  the  solar  spectrum,  it  soon  begins  to  blacken.  Buf 
it  does  not  blacken  with  equal  promptitude  in  each  of  the 
colored  spaces  ; the  effect  takes  place  most  rapidly  among 
the  more  refrangible  colors,  and  especially  in  the  violet  re^ 
gion.  As  in  the  case  of  heat,  the  effect  extends  far 
beyond  the  limit  of  the  spectrum,  and  where  the 
eye  can  not  discover  a trace  of  light.  We  may  be 
led,  therefore,  to  conclude  that  there  exists  in  the 
sunbeam  an  agent  capable  of  producing  chemical 
effects,  which  exerts  no  action  on  a thermometer, 
which  can  not  be  perceived  by  the  eye,  and  which, 
therefore,  is  neither  heat  nor  light. 

By  placing  mixtures  of  chlorine  and  hydrogen 
in  small  vials,  and  immersing  them  in  the  colored 
spaces,  we  can  readily  determine  the  place  of  max- 
imum action,  and  the  distribution  of  the  chemical  in- 
fluence throughout  the  spectrum.  In  this,  as  in  the 
former  instance,  the  greatest  effect  is  found  among 
the  more  refrangible  colors,  and  from  that  point 
diminishes  toward  each  extremity  of  the  spectrum. 

What  changes  does  chloride  of  silver  undergo  in  the  sunshine  ? When  a 
mixture  of  chlorine  and  hydrogen  is  exposed  to  the  sun,  what  occurs  ? How 
does  light  change  vegetable  colors?  Which  ray  darkens  the  chloride  of 
Silver  most  ? What  proof  have  we  that  another  agent  exists  in  the  sun’s 
r:i\s  l)esides  light  and  heat?  AVliat  ray  affects  the  mixture  of  chlorine  and 
liwlroion  most  i)Owerfully  ? 


Fig.  63. 


84 


FIXED  LINES. 


When  the  aperture  which  admits  a ray  of  light  into  the 
dark  room,  Fig.  60,  is  a narrow  fissure  or  slit,  not  more  than 
the  one  thirtieth  of  an  inch  in  width,  the  spectrum  which 
is  formed  by  the  action  of  a prism  is  crossed  by  great  num- 
bers of  black  lines.  These  always  are  found  in  the  same 
position,  as  respects  the  colored  spaces,  and,  from  the  in- 
variabihty  of  that  position,  are  much  used  as  boundary 
marks.  They  are  designated  by  the  letters  of  the  alphabet, 
and  their  relative  magnitude,  with  their  position,  is  given  in 
Fig.  63,  on  the  previous  page. 


LECTUEE  XIX. 

Wave  Theory  of  Light. — Proofs  of  the  Existence  of  the 
Ether. — Light  consists  of  Waves  in  it. — The  Ethereal 
Particles  move  hut  little. — Distinction  between  Vibra- 
tion and  Undulation. — FresneVs  Theory  of  Transverse 
Vibrations. — Transverse  and  Normal  Waves, — Brill- 
iancy of  Light  defends  on  Amplitude  of  Vibration. 

The  cause  of  light  is  an  undulatory  movement  taking 
place  in  the  ethereal  medium.  That  such  a medium  exists 
throughout  all  space,  seems  to  be  proved  by  a number  of  as- 
tronomical facts.  It  exerts  a resisting  agency  on  bodies 
moving  in  it.  From  its  tenuity,  we  should  scarcely  expect 
that  it  would  impress  any  disturbance  on  the  great  planetary 
masses  ; but  on  light,  gaseous  cometary  bodies,  it  produces 
a perceptible  action.  The  comet  of  Encke,  with  a period  of 
about  1200  days,  is  accelerated  in  each  revolution  by  about 
two  days  ; and  that  of  Biela,  with  a period  of  2460  days, 
is  accelerated  by  about  one  day.  As  there  is  no  other  ob- 
vious cause  for  these  results,  astronomers  have  very  gener- 
ally looked  upon  them  as  corroborative  proofs  of  the  exist- 
ence of  a resisting  medium,  that  universal  ether  to  which  so 
many  other  facts  point. 

In  this  elastic  medium,  undulatory  movements  can  be 
propagated  in  the  same  manner  as  waves  of  sound  in  the 
air.  It  is  to  be  clearly  understood  that  the  ether  and  light 
are  distinct  things  ; the  latter  is  merely  the  efiect  of  move- 

What  are  the  fixed  lines  ? How  are  these  lines  designated,  and  what  is 
their  use  ? What  proofs  have  we  of  the  existence  of  an  ethereal  medium  ? 
What  is  the  relation  between  the  ether  and  light  ? 


MECHANISM  OF  WAVES. 


85 


ments  in  the  former.  Atmospheric  air  is  one  thing,  and  the 
sound  which  traverses  it  another.  The  air  is  not  made  up 
of  the  notes  of  the  gamut,  nor  is  the  ether  composed  of  the 
seven  colors  of  light. 

Across  the  ether,  undulatory  movements,  resembling,  in 
many  respects,  the  waves  of  sound  in  the  atmosphere,  trav- 
erse with  prodigious  velocity.  From  the  eclipses  of  Jupi- 
ter’s satellites,  and  other  astronomical  phenomena,  it  appears 
that  the  rate  of  the  propagation  of  light,  or  the  velocity  with 
which  these  waves  advance,  is  192,000  miles  in  a second. 
We  are  not,  however,  to  understand  by  this  that  the  ethereal 
particles  rush  forward  in  a rectilinear  course  at  that  rate  : 
those  particles,  far  from  advancing,  remain  stationary. 

If  we  take  a long  cord,  a Fig.  64,  and  having  fastened 
it  by  the  extremity,  5,  to  g4 

a fixed  obstacle,  com-  | 

mence  agitating  the  end,  ^ ^ \ 

a,  up  and  down,  the  cord  | 

will  be  thrown  into  wave-  ^ 

like  motions,  passing  rapidly  from  one  end  to  the  other. 
This  may  afford  us  a rude  idea  of  the  nature  of  the  ethereal 
movements.  The  particles  of  which  the  cord  is  composed 
do  not  advance  or  retreat,  though  the  undulations  are  rap- 
idly passing. 

So,  too,  if  in  the  centre,  c,  of  a surface  of  water.  Fig. 
65,  we  make  a tapping  motion  with  the  Fig.  65. 

finger,  circular  waves  are  propagated, 
which,  expanding  as  they  go,  soon  reach 
the  sides  of  the  vessel  which  holds  the 
water.  A light  object  placed  on  the  sur- 
face is  not  violently  drifted  forward  by 
the  waves,  but  remains  entirely  motion- 
less. We  see,  therefore,  that  there  is  a 
wide  distinction  between  the  motion  of  a 
wave  and  the  motions  of  the  particles  among  which  it  is 
passing.  They  retain  their  places,  but  the  wave  flows 
rapidly  forward. 

A distinction  is  to  be  made  between  the  words  vibration 
and  undulation.  In  the  case  of  the  cord.  Fig.  64,  the  vi- 


At  what  rate  is  light  propagated  ? Do  the  ethereal  particles  move  forward 
at  that  rate  ? How  may  the  movements  of  ethereal  waves  be  represented 
by  a cord  ? How  may  they  be  represented  on  the  * surface  of  water?  Do 
the  vibrating  particles  move  forward  with  the  wave  ? 


86 


THEORY  OP  TRANSVERSE  VIBRATIONS. 


bration  is  represented  by  the  movement  exerted  by  the  hand 
at  the  free  extremity,  a ; the  undulation  is  the  wave-like 
motion  that  passes  along  the  cord.  In  the  case  of  the  wa- 
ter, Fig.  65,  the  vibration  was  represented  by  the  tapping 
motion  of  the  finger,  the  undulation  by  the  resulting  wave. 
We  therefore  see  that  these  stand  in  the  relaJ;ion  of  cause 
and  effect : the  vibration  is  the  cause,  and  the  undulation 
the  effect.  Throughout  the  ethereal  medium,  each  particle 
vibrates  and  transmits  the  undulatory  effect  to  the  particles 
next  beyond  it. 

In  the  same  way  as  a vibrating  cord  agitates  the  sur- 
rounding air,  and  makes  waves  of  sound  pass  through  it,  so 
does  an  incandescent  or  shining  particle,  vibrating  with  pro- 
digious rapidity,  impress  a wave-like  movement  on  the  ether, 
and  the  movement  eventually  impinging  on  the  eye  is  what 
we  call  light. 

To  refer  again  to  the  simple  illustration  given  in  Fig.  64  : 
it  is  obvious  that  there  are  an  infinite  variety  of  directions 
in  which  we  may  vibrate  that  cord  or  throw  it  into  undula- 
tions. We  may  move  it  up  and  down,  or  horizontally  right 
and  left,  and  also  in  an  infinite  number  of  intermediate  di- 
rections, every  one  of  which  is  transverse,  or  at  right  angles 
Fi^.ee.  to  the  length  of  the 

cord,  3is  a b bj  c c, 
&c..  Fig.  66.  This  is 
the  peculiarity  of  the 
movement  of  light.  Its 
vibrations  are  trans- 
verse to  the  course  of  the  ray ; and  in  this  it  differs  from 
the  movement  of  sound,  in  which  the  vibrations  are  normal, 
that  is  to  say,  executed  in  the  direction  of  the  resulting  wave, 
and  not  at  right  angles  to  it. 

This  great  discovery  of  the  transverse  vibrations  of  light 
was  made  by  M.  Fresnel.  It  is  the  foundation  of  the  whole 
theory  of  optics,  and  offers  a simple  but  brilliant  explana- 
tion of  so  many  of  the  phenomena  of  light,  that  the  undula- 
tory theory  is  by  many  writers  designated  the  Theory  of 
Transverse  Vibrations. 

It  may,  however,  be  remarked,  that  though  light  consists 


What  is  the  distinction  between  vibrations  and  undulations  ? How  does 
each  ethereal  particle  propagate  the  wave  to  those  beyond  it  ? Is  there  any 
analogy  between  sound  and  light  ? In  how  many  ways  may  a cord  be  vi- 
brated ? What  is  implied  by  the  term  theory  of  transverse  vibrations  ? 


COLORS  DEPEND  ON  WAVE-LENGTH. 


87 


of  rays  originating  in  these  transverse  motions,  it  is  not  im- 
possible that  there  may  be  other  phenomena  which  corre- 
spond to  movements  in  other  directions.  To  those  move- 
ments our  eyes  are  totally  blind,  and  hence  we  can  not 
speak  of  them  as  light.  In  the  same  way  there  may  be 
motions  in  the  air,  due  to  transverse  vibrations,  but  to  them 
our  ear  is  perfectly  deaf.  But  it  is  not  improbable  that  God 
has  formed  organs  of  vision  and  organs  of  hearing  in  the 
case  of  other  animals  upon  a different  type ; eyes  that  can 
perceive  normal  vibrations  in  the  ether,  and  ears  that  can 
distinguish  transverse  sounds  in  the  air. 

Lights  differ  from  each  other  in  two  striking  particulars 
— ^brilliancy  and  color.  These  are  determined  by  certain 
affections  or  qualities  in  the  waves.  On  the  surface  of  water 
we  may  have  a wave  not  an  inch  in  altitude,  or  a wave,  as 
the  phrase  is,  “mountains  high.”  Under  these  circum- 
stances, waves  are  said  to  differ  in  amplitude  ; and,  trans- 
ferring this  illustration  to  the  case  of  light,  a wave,  the  am- 
plitude of  which  is  great,  impresses  us  with  a sense  of  in- 
tensity or  brilliancy,  but  a wave,  the  amplitude  of  which  is 
little,  is  less  bright.  The  brilliancy  of  light  depends  on  the 
magnitude  of  the  excursions  of  the  vibrating  particles. 


LECTURE  XX. 

Wave  Theory  of  Light. — Colors  of  Light  deiiend  upon 
Wave  Lengths.  — Interference  of  Sounds.  — Young's 
Theory  of  Interference  of  Light. — Condition  of  Inter- 
ference.— Explanation  of  Lights  and  Shades  in  Shad- 
ows. 

By  the  length  of  a wave  upon  water,  we  mean  the  dis- 
tance that  intervenes  from  the  crest 

of  one  wave  to  that  of  the  next,  ox  a 5 

from  depression  to  depression.  Thus, 
in  Fig.  67,  from  a to  b,  or,  what  is 
the  same,  from  c to  cl,  constitutes  the  wave  length. 

In  the  ether  the  length  of  the  waves  determines  the  phe- 

Are  other  motions  possible  ? What  is  meant  by  the  amplitude  of  waves  ? 
On  what  does  the  brilliancy  of  light  depend  ? What  is  meiint  by  the  length 
of  a wave  ? 


88 


TWO  SOUNDS  PRODUCE  SILENCE. 


nomenon  of  color ; this  may  be  rigorously  proved,  as  we 
shall  soon  see,  when  we  come  to  the  methods  by  which  phi- 
losophers have  determined  the  absolute  lengths  of  undula- 
tions. It  has  been  found  that  the  longer  waves  give  rise 
to  red  light,  the  shorter  ones  to  violet,  and  those  of  interme- 
diate magnitudes  the  other  colors  in  the  order  of  their  re- 
frangibility. 

Two  rays  of  light,  no  matter  how  brilliant  they  are  sep- 
arately, may  be  brought  under  such  relations  to  one  another 
as  to  destroy  each  other’s  effect  and  produce  darkness.  Light 
added  to  light  may  produce  darkness.  Two  sounds  may 
bear  such  a relation  to  each  other  that  they  shall  produce 
silence  ; and  two  waves,  on  the  surface  of  water,  may  so  in- 
terfere with  one  another  that  the  water  shall  retain  its  hor- 
izontal position. 

Take  two  tuning  forks  of  the  same  note,  and  fasten  by  a 
QQ  little  sealing  wax  on  one  prong  of  each  a disc 
of  card-board,  half  an  inch  in  diameter,  as  seen 
Fig.  68,  a.  Make  one  of  the  forks  a little 
heavier  than  the  other,  by  putting  on  the  end 
of  it  a drop  of  the  wax. 

Then  take  a glass  jar,  b,  about  two  inches  in 
diameter  and  eight  or  ten  long,  and  having 
made  one  of  the  forks  vibrate,  hold  it  over  the 
mouth  of  the  jar,  as  seen  at  d,  its  piece  of  card-  , 
board  being  downward  ; commence  pouring  water  into  the 
jar,  and  the  sound  will  be  greatly  re-enforced.  It  is  the 
column  of  air  in  the  jar  vibrating  in  unison  with  the  fork, 
and  we  adjust  its  length  by  pouring  in  the  water ; when 
ilie  sound  is  loudest,  we  cease  to  pour  in  any  more  water, 
the  jar  is  adjusted,  and  we  can  now  prove  that  two  sounds 
added  together  may  produce  silence. 

It  matters  not  wliich  fork  is  taken,  whether  it  be  the  light 
or  the  loaded,  on  making  it  vibrate  and  holding  it  over  the 
mouth  of  the  resonant  jar,  we  hear  a uniform  and  clear 
sound,  without  any  pause,  stop,  or  cessation.  But  if  we 
make  both»vibrate  over  the  jar  together,  a remarkable  phe- 
nomenon arises,  a series  of  sounds  alternating  with  a series 
of  silences ; for  a moment  the  sound  increases,  then  dies 


What  is  the  connection  between  color  and  wave-length  ? What  is  meant 
by  the  interference  of  lights  or  of  sounds?  Give  an  illustration  of  the  in- 
terference of  sounds.  What  is  the  character  of  the  sound  which  the  re- 
sonant jar  emits  ? 


LAWS  OF  INTERFERENCE. 


89 


away  and  ceases,  then  swells  forth  again,  and  again  declines, 
and  so  it  continues  until  the  forks  cease  vibrating.  The 
length  of  these  pauses  may  be  varied  by  putting  more  or 
less  wax  on  the  loaded  fork ; and  as  we  can  see  that  even 
during  the  periods  of  silence  both  forks  are  rapidly  vibrating, 
the  experiment  proves  that  two  sounds  taken  together  may 
produce  silence. 

Under  these  circumstances,  waves  of  sound  are  said  to  in- 
terfere with  each  other,  and  in  like  manner  interference  takes 
place  among  the  waves  of  light.  We  can  gather  an  idea 
of  the  mechanism  by  considering  this  case  in  waves  upon 
water,  in  which,  if  two  undulations  encounter  under  such 
circumstances  that  the  concavity  of  the  one  corresponds  with 
the  convexity  of  the  other,  they  mutually  destroy  each  other’s 
effect. 

If  two  systems  of  waves  of  the  same  length  encounter 
each  other  after  having  come  through  paths  oi equal  length, 
they  will  not  interfere.  Nor  will  they  interfere  even  though 
there  be  a difference  in  the  length  of  these  paths,  pro- 
vided that  diflerence  be  equal  to  one  whole  wave,  or  two, 
or  three,  &c. 

But  if  two  systems  of  waves  of  equal  length  encounter 
each  other  after  having  come  through  paths  of  unequal 
length,  they  will  interfere,  and  that  interference  will  be  com-, 
plete  when  the  difference  of  the  paths  through  which  they 
have  come  is  half  a wave,  or  1 J,  2 J,  3J,  See. 

These  cases  are  respectively  shown  at  a and  c cl,  Fig- 


69,  at  the  point  of  encounter,  x ; in  the  Fig.  69. 

first  instance,  the  two  sets  of  waves  are  ^ cc  a 

in  the  same  phase,  that  is,  their  con- 

cavities  and  convexities  respectively  h 

correspond,  and  there  is  no  interfer-  ^ 

ence ; but  in  the  second  case,  at  the 

point  of  encounter,  x,  the  two  systems  ^ ^ 

are  in  opposite  phases,  the  convexity 


of  the  one  corresponding  with  the  concavity  of  the  other, 
and  interference  takes  place. 

Upon  these  principles,  we  can  account  for  the  remarka- 
ble results  of  the  following  experiment : From  a lucid  point. 


Why  are  there  pauses  in  it  ? At  the  time  of  these  pauses,  are  the  forks 
vibrating  ? When  two  waves  upon  water  encounter  each  other,  under  what 
circumstances  will  they  interfere  ? When  systems  of  waves  of  equal  length 
encounter  one  another,  when  do  they,  and  when  do  they  not,  interfere  ? 


90 


INTERFERENCE  OF  LIGHT. 


s,  Fig.  70,  which  may  be  formed  by  the  rays  of  the  sun 
Fisr.  70.  converged  by  a double  convex  lens  of 

short  focus,  or  by  passing  a sunbeam 
^ through  a pinhole,  let  rays  emanate, 
0 and  in  them  place  the  opaque  obsta- 
e cle,  a bj  which  we  will  suppose  to  be 
a cylindrical  body,  seen  endwise  in  the 
figure  ; at  some  distance  beyond  place 
. a screen  of  white  paper,  c to  receive 
^ the  shadow.  It  might  be  supposed 
that  this  shadow  should  be  of  a magnitude  included  between 
% y,  because  the  rays,  s a,  s b,  which  pass  the  sides  of  the 
obstacle,  impinge  on  the  paper  at  those  points.  It 
° ' might  farther  be  supposed,  that  within  the  space  x y 

the  shadow  should  be  uniformly  dusky  or  dark  ; but, 
on  examining  it,  such  will  not  be  found  to  be  the 
case.  The  shadow  will  be  found  to  consist  of  a se- 
ries of  light  and  dark  stripes,  as  represented  in  Fig. 
71.  In  its  middle,  at  e,  Figs.  70  and  71,  there  is  a 
white  stripe  ; this  is  succeeded  on  each  side  by  a dark 
one ; this,  again,  by  a bright  one,  and  so  on  alternately. 
Upon  the  undulatory  theory,  all  this  is  readily  explained. 
Sounds  easily  double  round  a corner,  and  are  heard  though 
an  obstacle  intervenes.  Waves  upon  water  pass  round  to 
the  back  of  an  object  on  which  they  impinge,  and  the  undu- 
lations of  light  in  the  same  manner  flow  round  at  the  back 
of  the  piece  of  wire,  a by  Fig.  7 0 ; and  now  it  is  plain  that 
two  series  of  waves  which  have  passed  from  the  sides  of  the 
obstacle  to  the  middle  of  its  shadow,  that  is,  along  the  lines 
aCyb  6y  have  gone  through  paths  of  equal  length,  and,  there- 
fore, when  they  encounter  at  the  point  e,  they  will  not  in- 
terfere, but  exalt  each  other’s  effect. 

But,  leaving  this  central  point,  e,  and  passing  \o  fy  it  is 
plain  that  the  systems  of  waves  which  have  come  through 
the  paths  a fy  b f,  have  come  through  different  distances, 
.for  b fh  longer  than  a f ; and  if  this  difference  be  equal  to 
the  length  of  half  a wave,  they  will,  when  they  encounter 
at  the  point  fy  interfere  and  destroy  each  other,  and  a dark 
stripe  results. 


Describe  the  experiment  represented  in  Fig.  70.  Is  the  resulting  shadow 
uniformly  dark  ? At  the  central  point  of  the  shadow,  is  it  dark  or  light  ? 
Explain  the  cause  of  this  central  light  space,  and  of  the  alternate  dark  and 
light  ones  on  each  side  of  it. 


LENGTH  OF  WAVES. 


91 


Beyond  this,  at  the  point  gy  the  waves  from  each  side  of 
the  obstacles,  a g,  b gy  again  have  come  through  unequal 
paths  ; but,  if  the  difference  is  equal  to  the  length  of  one 
whole  wave,  they  will  not  interfere,  and  a white  stripe  re- 
sults. 

Reasoning  in  this  manner,  we  can  see  that  the  interior 
of  such  a shadow  consists  of  illuminated  and  dark  spaces 
alternately : illuminated  spaces,  when  the  light  has  come 
through  paths  that  are  equal,  or  that  differ  from  each  other 
by  1,  2,  3,  4,  . . &c.,  waves  ; and  dark,  when  the  difference 
between  them  is  equal  to  J,  IJ,  2^y  3J,  . . &c.,  waves. 

That  it  is  the  interference  of  the  light  coming  from  the 
opposite  sides  of  the  opaque  object  which  is  the  cause  of 
these  phenomena,  is  proved  by  the  circumstance  that  if  we 
place  an  opaque  screen  on  one  side  of  the  obstacle,  so  as  to 
prevent  the  light  passing,  the  fringes  all  disappear. 


LECTURE  XXI. 

Wave  Theory  of  Light. — Measurement  of  the  Length  of 
a Wave  of  Light. — Length  differs  for  different  Colors. 
— Measurement  of  the  Period  of  Vibrations. — Nature 
of  Polarized  Light. — Plane y Circular y and  Elliptical 
Polarized  Light. — Reflection,  Refraction,  and  Absorp- 
tion of  Light. 

The  experiment.  Fig.  70,  may  enable  us  to  determine 
the  length  of  a wave  of  light.  This  may  be  readily  done 
by  measuring  the  distances  af  and  b f or  from  the  sides  of 
the  obstacle  to  the  first  bright  stripe  from  the  central  one, 
for  at  that  point  the  difference  between  those  two  lines,  af 
and  b f is  equal  to  the  length  of  one  wave.  We  might  em- 
ploy the  second  bright  stripe  ; the  difference  then  would  be 
equal  to  two  waves. 

Farther,  if,  instead  of  using  ordinary  white  light,  radia- 
ting from  the  lucid  point,  s,  we  use  colored  lights,  such  as 
red,  yellow,  blue,  &c.,  in  succession,  we  shall  find  that  the 


What  is  the  length  of  the  paths  of  the  waves  which  go  to  the  illuminated 
spaces,  and  of  those  which  go  to  the  dark  ones  ? How  can  it  be  proved  that 
the  waves  from  the  opposite  sides  of  the  obstacle  interfere  ? How,  by  this 
arrangement,  might  we  measure  the  length  of  a wave  of  light  ? 


92 


FREaUENCY.OF  WAVE- VIBRATION. 


wave  length  determined  by  the  process  just  explained  dif 
fers  in  each  case  ; that  it  is  greatest  in  red,  and  smallest  in 
violet  light.  By  exact  experiments  made  upon  methods 
more  complicated  than  the  elementary  one  here  given,  it 
has  been  found  that  the  different  colored  rays  of  light  have 
waves  of  the  following  length  : 


JVave  Lengths  of  the  Different  Colors  of  Light. 

The  English  inch  is  supposed  to  be  divided  into  ten  mill- 
ions of  equal  parts  and  of  those  parts  the  wave  lengths  are  : 


For  red  light  . 

. . 256 

“ orange  . . 

. . . 240 

“ yellow  . . 

. . . 227 

“ green  . . 

. . . 211 

For  blue  .....  196 

“ indigo 185 

“ violet 174 


In  this  manner,  it  is  proved  that  the  different  colors  of 
light  arise  in  the  ether  from  its  being  thrown  into  waves 
of  different  lengths. 

Knowing  the  rate  at  which  light  is  propagated  in  a sec- 
ond, and  the  wave  length  for  a particular  color,  we  can 
readily  tell  the  number  of  vibrations  executed  in  a second, 
for  they  plainly  are  obtained  by  dividing  192,000  miles,  the 
rate  of  propagation,  by  the  wave  length.  From  this  it  ap- 
pears, that  if  a single  second  of  time  be  divided  into  one 
million  of  equal  parts,  a wave  of  red  light  trembles  or  pul- 
sates 458  millions  of  times  in  that  inconceivably  short  in- 
terval, and  a wave  of  violet  light  727  millions  of  times. 

In  speaking  of  the  constitution  of  matter  in  Lectures  I. 
and  II.,  I had  occasion  to  allude  to  the  amazingly  minute 
scale  on  which  it  is  constructed.  The  remarkable  facts  we 
are  now  considering  are  a monument  to  the  genius  of  New- 
ton and  his  successors,  for  they  give  us  a just  idea  of  the 
scale  of  space  and  time  upon  which  Nature  carries  on  her 
works  among  the  molecules  of  matter. 

Common  light,  as  has  been  said,  originates  in  vibratory 
motions  taking  place  in  every  direction  transverse  to  the  ray. 
With  polarized  light  it  is  different ; to  gather  an  idea  of  the 
nature  of  polarized  light,  we  must  refer  once  more  to  the 
cord.  Fig.  66,  which,  as  has  been  said,  serves  to  imitate 
common  light  when  its  extremity  is  vibrated  vertically,  hor- 


When  different  colors  of  light  are  used,  are  the  waves  found  to  be  of  equal 
length  ? What  is  the  length  of  a wave  of  red  and  of  violet  light  respective- 
ly ? How  can  we  ascertain  the  number  of  vibrations  in  a second  ? On  the 
undulatory  theory,  in  what  direction  do  the  ethereal  particles  vibrate  in  the 
case  of  common  light  ? What  is  the  case  in  polarized  light  ? 


POLARIZATION  OF  LIGHT. 


93 


izontally,  and  in  all  intermediate  positions  in  rapid  succes- 
sion. But  if  we  simply  vibrate  it  up  and  down,  or  right  and 
left,  then  it  imitates  polarized  light ; polarized  light  is,  there- 
fore, caused  by  vibrations  transverse  to  the  ray,  but  which 
are  executed  in  one  direction  only. 

There  is  a certain  gem,  the  tourmaline,  which  serves  to 
exhibit  the  properties  of  polarized  light.  If  we  take  a thin 
plate  of  this  substance,  c d,  prop-  Fig.  72. 

erly  cut  and  polished,  and  allow  M 
a ray  of  light,  a b,  Fig.  72,  to  ^ j|l 

fall  upon  it,  that  ray  will  be  free- |j! 

ly  transmitted  through  a second  L| 
plate  if  it  be  held  symmetrically 
to  the  first,  as  shown  at  e f ; but  if  we  turn  the  second  plate 
a quarter  round,  as  seen  at  g h,  then  the  light  can  not  pass 
through.  The  rays  of  the  meridian  sun  can  not  pass  through 
a pair  of  crossed  tourmalines. 

The  cause  of  this  is  obvious : if  we  take  Fig.  73. 
a thin  lath  or  strip  of  pasteboard,  c Fig.  i d 

73,  and  hold  it  before  a ^ge,  or  grate,  ab,  c ' ^ 

it  will  readily  slip  through  when  its  plane  [ 
coincides  with  the  bars  ; but  if  we  turn  it 
a quarter  round,  as  at  e then  of  course 
it  can  not  pass  the  bars. 

Now  the  plate  of  tourmaline.  Fig.  72,  c dy  polarizes  the 
light,  a by  which  falls  upon  it , that  is,  the  waves  that  pass 
through  it  are  vibrating  all  in  one  plane.  They  pass,  there- 
fore, readily  through  a second  plate  of  the  same  kind,  so 
long  as  it  is  held  in  such  a way  that  its  structure  coincides 
with  that  motion,  but  if  it  be  turned  round  so  as  to  cross 
the  waves,  then  they  are  unable  to  pass  through  it. 

There  are  many  ways  in  which  light  can  be  polarized  : 
by  reflection,  refraction,  double  refraction,  &c.  The  result- 
ing motion  impressed  on  the  ether  is  the  same  in  all  cases. 

Light  modified  as  just  described  is  designated  plane  po- 
larized light ; but  there  are  other  varieties  of  polarization. 
If  the  end  of  the  rope.  Fig.  66,  be  moved  in  a circle,  circular 
waves  will  be  produced,  imitating  circularly  polarized  light ; 
and  if  it  be  moved  in  an  ellipse,  elliptical  polarized  light. 


Describe  the  optical  properties  of  the  tourmaline.  Give  an  illustration  of 
the  phenomenon.  What  is  the  cause  of  the  action  of  the  second  tourmaline 
plate?  Mention  some  of  the  methods  by  which  light  may  be  polarized. 
What  is  circularly  polarized  light  ? What  is  elliptically  polarized  light  ? 


94 


LAWS  OF  REFLECTION  AND  REFRACTION. 


The  undulatory  theory  of  light  gives  a clear  account  of 
the  ordinary  phenomena  of  optics.  The  general  law  under 
Fig.  74.  which  light  is  reflected  from  polished  surfaces 
is  a direct  consequence  of  it ; that  law  is  : 
that  the  angle,  deb,  Fig.  74,  made  by  the 
reflected  ray,  d c,  with  a perpendicular,  c b, 
drawn  to  the  point  c,  at  which  the  light  im- 
pinges, is  equal  to  the  angle,  a c b,  which  the 
incident  ray  makes  with  the  same  perpendic- 
ular, or,  as  it  is  briefly  expressed,  “ the  angles  of  incidence 
and  reflection  are  equal  to  each  other,  and  on  opposite  sides 
of  the  perpendicular.” 

By  the  aid  of  this  law,  we  can  show  the  action  of  reflect- 
ing surfaces  of  any  kind,  and  discover  the  properties  of  plane 
and  curved  mirrors,  whether  they  be  concave  or  convex, 
spherical,  elliptical,  paraboloidal,  or  any  other  figures. 

From  the  undulatory  theory,  the  law  of  the^  refraction  of 
light  also  follows  as  a necessary  consequence.  It  is : “ in 
every  transparent  substance,  the  sines  of  the  angles  of  in- 
cidence and  refraction  are  to  each  other  in  a constant  ratio 
and  by  the  aid  of  this  law  we  can  determine  the  action  of 
media  bounded  by  surfaces  of  any  kind,  plane  or  spherical, 
concave  or  convex.  It  explains  the  action  of  lenses,  and  the 
construction  of  refracting  telescopes  and  microscopes. 

Sir  Isaac  Newton’s  discovery,  that  white  light  arises  from 
the  mixture  of  the  different  colored  rays  in  certain  propor- 
tions, explains  the  cause  of  the  colors  which  transparent 
media  often  exhibit ; thus,  if  glass  be  stained  with  the  oxide 
of  cobalt,  it  allows  a blue  light  to  pass  it,  and  upon  such 
principles  the  art  of  painting  on  glass  depends  ; different 
colors  being  communicated  by  different  metallic  oxides. 
The  cause  of  this  effect  is  readily  discovered  ; for,  if  we 
make  the  light  which  enters  a dark  room,  as  in  Fig.  60, 
pass  through  such  a piece  of  stained  glass  before  it  goes 
through  the  prism,  and  examine  the  resulting  spectrum,  we 
find  that  several  rays  are  wanting  in  it ; that  the  glass  has 
absorbed  or  detained  some,  and  allowed  others  to  traverse  it. 
A piece  of  blue  glass  thus  suffers  most  of  the  blue  light  to 
pass,  but  stops  the  green,  the  yellow,  &c.  But  it  is  also  to 
be  observed,  that  the  light  which  is  transmitted  by  any  of 


What  is  the  general  law  of  reflection  ? What  is  the  law  of  the  refraction 
of  light?  WTiat  is  the  cause  of  the  colors  of  transparent  media?  Is  the 
light  transmitted  through  these  colored  media  pure  ? 


PRODUCTION  OF  LIGHT. 


95 


these  colored  media  is  not  pure,  it  is  contaminated  with 
other  tints  ; the  blue  glass,  for  instance,  does  not  stop  all 
the  rays  except  the  blue ; it  allows  a large  portion  of  the 
red  to  pass,  and  hence  the  light  it  transmits  is  more  or  less 
compound. 


LECTURE  XXII. 

• Production  of  Light.  — By  Incandescence.  — Point  at 
which  Bodies  are  Red  Hot.  — All  Solids  shine  at  the 
same  Degree.  — Colors  Emitted. — Rate  of  Brilliancy. 
— Nature  of  Flames.  — Phosphorescence.  — Controlled 
by  Temperature. 

A theoretical  explanation  of  the  chemical  action  of 
light  must  depend  on  the  views  entertained  of  the  nature 
of  that  agent.  In  a series  of  memoirs,  published  in  the  Lon- 
don and  Edinburgh  Philosophical  Magazine  between  the 
years  1847  and  1851, 1 have  investigated  the  circumstances 
under  which  light  arises  by  artificial  processes,  and  shall 
here  proceed  to  detail  the  chief  results. 

There  are  three  general  processes  by  which  light  is  ob- 
tained artificially:  1st.  By  the  ignition  of  bodies;  2d.  By 
their  combustion  or  burning  ; 3d.  By  phosphorescence. 

1st.  Of  the  Production  of  Light  by  Ignition. — All  sohd 
substances  shine  when  their  temperature  is  raised  to  a cer- 
tain degree.  The  point  at  which  this  occurs  has  been  vari- 
ously estimated.  Sir  Isaac  Newton  places  it  at  635° ; 
Davy,  at  812°  ; Wedge  wood,  at  947°  ; Daniell,  at  980°. 
By  taking  advantage  of  the  improved  means  which  the  pres- 
ent state  of  science  offers,  I found  that  for  platinum  it  is 
977°,  or,  if  Laplace’s  coefficient  of  dilatation  be  used  in  the 
calculation,  1006°. 

By  inclosing  a number  of  different  substances  with  a mass 
of  platinum  in  a gun-barrel,  the  temperature  of  which  was 
gradually  raised,  it  was  found,  on  looking  down  the  barrel, 
that  they  all  commenced  to  shine  at  the  same  moment,  and 
this  even  though,  as  in  the  case  of  lead,  the  melted  condi- 
tion had  been  assumed.  I therefore  infer  that  all  solids  and 
liquids  begin  to  shine  at  the  same  degree  of  the  thermometer. 


What  is  the  temperature  of  ignition  ? Do  all  substances  shine  at  the  same 
degree  ? 


96 


LIGHT  BY  COMBUSTION. 


The  color  of  the  light  which  the  ignited  substance  emits 
depends  upon  the  degree  of  heat  to  which  it  is  exposed. 
Making  due  allowance  for  the  physiological  imperfections 
of  the  eye,  there  can  be  no  doubt  that  the  first  rays  which 
appear  are  the  red,  and  as  the  temperature  is  made  grad- 
ually to  go  up,  the  yellow,  orange,  green,  blue,  indigo,  and 
violet  are  emitted  in  succession.  At  2130°  all  these  colors 
are  exhibited,  and  from  their  commixture  the  substance  ap- 
pears white  hot. 

It  may  therefore  be  inferred,  that  as  the  temperature  of 
an  incandescent  body  rises,  it  emits  rays  of  light  of  an  in- 
creasing refrangibility. 

By  the  aid  of  the  method  of  extinction  of  shadows  it  was 
proved,  that  as  the  temperature  of  an  ignited  solid  rises,  the 
intensity  of  the  light  increases  very  rapidly.  For  example, 
platinum  at  2600°  emits  almost  forty  times  as  much  light 
as  it  does  at  1900°,  as  the  following  table  shows : 

Intensity  of  Light  emitted  hy  Platinum  at  different 
Temjperatures. 


Temperature  of  the  Platinum. 

Intensity  of  its  Light. 

980^  . . . 

000 

1900  . . . 

0*34 

2015  . . . 

0-62 

2130  . . . 

1*73 

2245  . . . 

2-92 

2360  . . . 

4*40 

2475  . . . 

7-24 

2590  . . . 

12-34 

From  a parallel  series  of  experiments,  in  which  the  heat 
radiated  by  the  ignited  platinum  was  measured,  a striking 
analogy  between  the  two  agents  appears.  Thus,  if  the 
quantity  of  heat  radiated  by  platinum  at  980°  be  taken  as 
unity,  it  will  have  increased  at  1440°  to  2*5  ; at  1900°  to 
7*8  ; at  2360°  to  17*8  nearly.  The  rate  of  increase  is,  there- 
fore, very  rapid,  as  in  the  preceding  case. 

2d.  Of  the  Production  of  Light  hy  Combustion. — It  has 
been  long  known  that  all  common  flames  are  incandescent 
shells,  the  interior  of  which  is  dark,  and  it  has  been  sup- 
posed that  there  are  certain  flames  which  emit  particular 
rays  only,  but  an  examination  by  the  prism  showed  that  in 
every  flame  every  prismatic  color  is  found.  The  red  which 

What  is  the  order  in  which  the  colored  rays  arc  emitted  ? At  what  rate 
does  the  brilliancy  of  the  light  increase  ? Does  the  same  hold  good  for  the 
radiant  heat  ? What  is  the  condition  of  the  interior  of  a flame  ? 


LIGHT  BY  COMBUSTION.  97 

burning  cyanogen,  and  the  blue  which  burning  sulphur 
emits,  are  compound  colors. 

By  burning  solid  carbon  in  oxygen  gas,  it  appeared  that 
there  is  a connection  between  the  refrangibility  of  the  light 
which  a burning  body  yields  and  the  intensity  of  the  chem- 
ical action  going  on,  and  that  the  refrangibility  always  in- 
creases as  the  chemical  action  increases. 

From  this  it  appears  that  flames,  such  as  those  of  lamps 
and  candles,  consist  of  a series  of  concentric  and  differently 
colored  shells,  the  most  interior  one  being  red,  and  having  a 
temperature  of  977°.  Upon  this,  in  succession,  are  placed 
orange,  yellow,  green,  blue,  indigo,  and  violet  shells.  The 
flame,  looked  at  directly,  appears  to  yield  white  light,  be- 
cause of  the  commixture  of  these  rays  ; but,  on  being  sub- 
mitted to  the  action  of  a prism,  they  are  separated  from  each 
other,  and  their  individual  existence  proved.  If,  therefore, 
we  could  isolate  a horizontal  section  of  such  a flame,  it 
would  have  the  aspect  of  an  iris  or  rainbow  ring. 

Upon  the  principle  that,  the  more  energetic  the  chemical 
action,  the  higher  the  refrangibility  of  the  light  emitted,  we 
may  explain,  without  difficulty,  the  colors  which  different 
flames  present.  The  red  tints  predominate  in  the  flame  of 
burning  cyanogen,  because  in  that  gas  there  is  an  element 
wholly  incombustible — the  nitrogen.  This,  as  it  is  set  fre 

cuts  off  the  free  access  of  the  air,  and  the  burning  goes  on 
tardily — very  much  in  the  same  manner  as  in  an  oil  lamp  to  , 
which  the  air  is  imperfectly  supplied.  On  the  other  hand, 
carbonic  oxide  burns  blue,  because  of  the  small  quantity  of 
air  required  to  carry  it  to  its  maximum  of  oxydation.  The 
color  of  flames  depends,  therefore,  on  the  completeness  or  in- 
completeness of  the  combustion ; this  principle  readily  ac- 
counting for  those  cases  in  which  means  are  used  for  retard- 
ing or  promoting  the  rate  of  burning,  as  where  an  atmos- 
phere of  oxygen  is  used,  or  air  introduced  into  the  interior 
of  a flame  by  means  of  a blowpipe,  the  bright  blue  cone 
arising  in  this  latter  instance  being  a striking  indication  of 
the  increased  rapidity  of  combustion. 

There  is,  therefore,  a direct  connection  between  the  ve- 
hemence with  which  chemical  affinity  is  satisfied  and  the 
refrangibility  of  the  resulting  light.  If,  as  there  are  many 
reasons  for  supposing,  all  chemical  changes  are  attended  by 

What  is  the  structure  of  a flame  ? Explain  the  cause  of  the  colors  of 
flames.  Why  is  the  blowpipe  cone  blue  ? 

E 


98 


PHOSPHORESCENCE. 


vibratory  movements  of  the  particles  of  the  bodiej  engaged 
it  might  well  be  anticipated  that  these  vibrations  should  in 
crease  in  frequency  as  the  action  becomes  more  violent. 
But  it  is  to  be  remembered  that  an  increased  frequency  of 
vibration  is  the  same  thing  as  an  increased  refrangibility. 

3d.  Of  the  Production  of  Light  hy  Phosphorescence. — 
All  solid  substances,  except  the  metals,  possess  the  property 
of  shining  after  they  have  been  exposed  to  the  sun.  In  some, 
the  effect  lasts  but  for  a moment ; in  others,  it  is  of  longer 
duration  and  considerable  splendor.  Among  the  best  phos- 
phor! may  be  mentioned  the  sulphuret  of  barium,  the  sul- 
phuret  of  calcium,  certain  varieties  of  fiuor  spar,  and  of  dia- 
mond. Phosphorescence  has  generally  been  regarded  as 
unattended  by  the  emission  of  heat. 

By  suitable  experimental  arrangements,  I ascertained  that 
the  best  phosphori,  when  at  their  maximum  of  glow,  do  not 
increase  in  volume  by  so  much  as  the  part ; but  that 

there  is  minute  expansion  can  not  be  doubted,  since,  when 
means  sufficiently  delicate  are  resorted  to,  a feeble  rise  of 
temperature  can  be  detected.  The  intensity  of  the  light 
disengaged  is  to  some  extent  deceptive  ; for,  by  resorting  to 
the  method  of  the  extinction  of  shadows,  it  was  shown  that 
a fine  specimen  of  chlorophane,  at  its  maximum  of  bright- 
ness, yielded  a light  three  thousand  times  less  intense  than 
the  flame  of  a very  small  oil  lamp. 

The  quantity  of  light  a substance  can  receive  when  e^f- 
posed  to  the  sun  depends  upon  the  temperature.  The  colder 
the  phosphorus  is,  the  more  brightly  will  it  subsequently 
shine.  If  kept  hot  during  its  exposure,  it  will  not  shine  at 
all.  If  a diamond  placed  upon  ice  is  submitted  to  the  sun, 
and  then  brought  into  a dark  room,  the  temperature  of  which 
is  60°,  for  a time  there  is  a glow,  but  presently  the  light 
declines  and  dies  out.  Let  the  diamond  now  be  put  in 
water  at  100°  ; again  it  shines,  and  again  its  light  dies  away, 
tf  it  next  be  removed  from  that  water  and  suffered  to  cool, 
and  then  be  reimmersed,  it  will  not  shine  again  ; but  if  the 
water  be  heated  to  200°,  and  the  diamond  be  dropped  into 
it,  again  it  glows,  and  again  its  light  dies  away.  There  is, 
therefore,  a correspondence  between  the  light  disengaged 
and  the  temperature  applied. 

What  is  the  connection  between  chemical  affinity  and  refrangibility 
What  substances  exhibit  phosphorescence  ? Do  phosphorescent  bodies  ex 
pand  ? What  is  the  actual  intensity  of  the  light  of  phosphori  ? How  is  phos 
phorescence  controlled  by  temperature  ? 


CHEMICAL  ACTION  OF  LIGHT. 


99 


The  phenomena  of  phosphorescence  may  all  be  explained 
on  the  principles  of  the  theory  of  undulations  ; for  from  a 
shining  body  undulations  are  propagated  in  the  ether,  and 
these,  impinging  on  a phosphorescent  surface,  throw  its  mole- 
cules into  a vibratory  movement.  These,  in  their  turn,  im- 
press on  the  ether  undulations  ; but,  by  reason  of  the  differ- 
ence of  its  density,  compared  with  that  of  the  molecules, 
they  do  not  lose  their  motion  at  once,  but  it  continues  for  a 
time  gradually  declining  away,  and  ceasing  when  the  vis 
viva  of  the  molecules  is  exhausted. 

We  may  therefore  abandon  expressions  derived  from  the 
material  theory  of  light,  such  as  the  absorption  and  subse- 
quent emission  of  the  luminous  agent,  and  conclude  that, 
whenever  a radiation  falls  upon  a surface  of  any  kind,  it 
throws  the  particles  thereof  into  a state  of  vibration,  as  when 
a stretched  string  is  made  to  vibrate  in  sympathy  with  a 
distant  musical  sound.  This  view  includes  at  once  all  the 
facts  of  the  radiation  of  heat  and  the  theory  of  calorific  ex- 
changes ; it  also  offers  an  explanation  of  the  connection  of  the 
atomic  weights  of  bodies  and  their  specific  heats.  It  sug- 
gests that  all  cases  of  the  decomposition  of  compound  mole- 
cules, under  the  influence  of  light,  is  owing  to  a want  of 
consentaneousness  in  the  vibrations  of  the  impinging  ray  and 
those  of  the  molecular  group,  which,  unable  to  maintain  it- 
self, is  broken  down,  under  the  periodic  impulses  it  is  receiv- 
ing, into  other  groups,  which  can  vibrate  along  with  the  ray 


LECTURE  XXIII. 

Chemical  Action  op  Light. — Action  of  Natural  and  Ar- 
tificial Lights. — Preliminary  Absorption. — Change  in 
the  Ray.  — Necessity  of  Absorption.  — The  Daguerreo- 
type.— Explanation  of  the  Process. — Its  Imperfections 
— Other  Processes. 

When  a solar  spectrum  falls  upon  paper  covered  over 
with  chloride  of  silver,  the  chloride  turns  black  in  the  more 
refrangible  regions.  The  darkening  effect  of  light  was 
known  to  the  alchemists.  The  bleaching  action  on  vegeta- 
ble colors  must  have  been  observed  from  the  earliest  times, 


On  what  principles  may  phosphorescence  be  explained  ? 


100 


CHEMICAL  ACTION  OF  LIGHT. 


but  it  is  only  recently  that  the  phenomenon  has  been  more 
particularly  investigated. 

From  whatever  source  it  may  he  derived,  light  exerts 
chemical  action.  The  moonbeams  are  sufficiently  intense 
to  give  copies  of  that  satellite  on  sensitive  surfaces,  as  I found 
in  1841.  Lamplight  and  other  artificial  lights  are  often 
peculiarly  energetic.  These  decomposing  effects  take  place 
on  those  portions  of  the  substance  only  on  which  the  rays 
actually  fall.  There  is  no  lateral  spreading,  nothing  analo- 
gous to  conduction. 

When  a sensitive  substance  receives  light  for  a short  space 
of  time,  no  change  takes  place,  the  rays  are  being  actively 
absorbed ; but  as  soon  as  that  preliminary  absorption  is  over, 
they  act  in  a manner  which  is*  perfectly  definite  ; if,  for  in- 
stance, it  be  a decomposition  they  are  bringing  about,  the 
amount  of  decomposing  effect  will  be  precisely  proportional 
to  the  quantity  of  rays  absorbed. 

When  a beam  from  any  shining  source  causes  a decom- 
posing efiect,  it  is  always  itself  disturbed ; the  medium 
which  is  changing  impresses  a change  on  the  ray.  Thus, 
a mixture  of  chlorine  and  hydrogen  unites  under  the  influ- 
ence of  a ray,  but  that  portion  of  the  ray  which  passes 
through  the  mixture  has  lost  the  quality  of  ever  bringing 
about  a like  change  again. 

•When  a beam  from  any  shining  source  falls  on  a change- 
able medium,  a portion  of  it  is  absorbed  for  the  purpose  of 
effecting  the  change,  and  the  residue  is  either  reflected  or 
transmitted,  and  is  perfectly  inert  as  respects  the  medium 
itself. 

No  chemical  effect  can  therefore  be  produced  by  such 
rays  except  they  be  absorbed.  It  is  for  this  reason  that  wa- 
ter is  never  decomposed  by  the  sunshine,  nor  oxygen  and 
hydrogen  made  to  unite ; for  these  substances  are  all  trans- 
parent, and  allow  the  rays  to  pass  without  any  absorption, 
and  absorption  is  absolutely  necessary  before  chemical  ac- 
tion can  ensue. 

But  with  chlorine  the  case  is  very  different.  This  sub- 
stance exerts  a powerful  absorbent  action  on  light ; the  ef- 
fect takes  place  on  the  more  refrangible  rays  ; when  mixed 


Give  examples  of  the  chemical  action  of  light.  Do  artificial  lights  possess 
that  property  ? What  is  meant  by  preliminary  absorption  ? What  change 
is  impressed  on  the  ray  ? Does  the  ray  undergo  absorption  ? Why  can  not 
water  be  decomposed  in  the  sunshine  ? 


PHOTOGENIC  PORTRAITS.  101 

with  hydrogen  and  set  in  the  light,  it  unites  with  a violent 
explosion. 

The  process  of  the  Daguerreotype  is  conducted  as  follows : 
A piece  of  silver  plate  is  brought  to  a high  polish  by  rub- 
bing it  with  powders,  such  as  Tripoli  and  rotten-stone,  every 
care  being  taken  that  the  surface  shall  be  absolutely  pure 
and  clean,  a condition  obtained  in  various  ways  by  different 
artists,  as  by  the  aid  of  alcohol,  dilute  nitric  acid,  &c.  This 
plate  is  next  exposed  in  a box  to  the  vapor  which  rises  from 
iodine  at  common  temperatures,  until  it  has  acquired  a gold- 
en yellow  tarnish ; it  is  next  exposed,  in  the  camera  obscura, 
to  the  images  of  the  objects  it  is  designed  to  copy,  for  a suit- 
able space  of  time.  On  being  removed  from  the  instrument, 
nothing  is  visible  upon  it ; but  on  exposing  it  to  the  fumes 
of  mercury,  the  images  slowly  evolve  themselves. 

To  prevent  any  farther  change,  the  tarnished  aspect  of 
the  plate  is  removed  by  washing  the  plate  in  a solution  of 
hyposulphite  of  soda,  and  finishing  the  washing  with  wa- 
ter ; it  can  then  be  kept  for  any  length  of  time. 

Several  important  improvements  on  the  original  process 
have  been  made  : 1st,  by  exposing  the  plate,  after  it  has 
been  iodized,  to  the  vapor  of  bromine,  or  chloride  of  iodine, 
which  gives  it  a wonderful  sensibility  ; 2d,  by  gilding  the 
plate,  after  the  other  operations  are  complete,  by  the  aid  of 
a mixture  of  hyposulphite  of  soda  and  chloride  ol  gold  ; this 
acts  like  a varnish,  fastening  the  picture,  and  giving  it  a 
more  agreeable  yellow  tone. 

The  art  of  taking  portraits  from  the  life,  which  has  now 
become  a branch  of  industry,  was  invented  by  me  soon  after 
the  Daguerreotype  was  known  in  America  ; at  that  time, 
this,  which  is  by  far  the  most  valuable  application  of  the 
chemical  agencies  of  light,  was  looked  upon  in  Europe  as 
entirely  beyond  the  powers  of  this  process  ; but  subsequent- 
ly great  improvements  in  it  have  been  made.  My  memoir 
descriptive  of  the  art  may  be  seen  in  the  London  and  Ed- 
inburgh Philosophical  Magazine  (September,  1840),  and 
the  facts  are  also  specified  in  the  Edinburgh  Review  (Jan- 
uary, 1843),  in  which  the  discovery  is  attributed  to  its  proper 
source,  the  author  of  this  book. 


Why  do  chlorine  and  hydrogen  explode  ? Describe  the  process  of  the 
Daguerreotype.  Are  the  images  visible  at  first?  By  what  means  are  they 
brought  out  ? How  is  the  picture  preserved  from  farther  change  ? MeO'. 
tion  some  of  the  later  improvements  of  the  process. 


102  CHEMICAL  ACTION  OF  LIGHT. 

When  a beam  falls  upon  the  surface  of  a Daguerreotype 
plate,  it  communicates  to  the  iodide  of  silver  a tendency  to 
decomposition,  but  iodine  is  never  set  free  because  of  the 
metallic  silver  behind.  On  exposing  a surface  disturbed  in 
this  manner  to  the  vapors  of  mercury,  entire  decomposition 
of  the  iodide  ensues,  its  silver  unites  with  the  mercury,  form- 
ing a white  amalgam,  and  the  iodine  corrodes  the  metallic 
silver  behind.  The  utmost  care  must  be  taken  in  all  Da- 
guerreotype processes  to  have  no  vapors  of  iodine,  or  bro- 
mine, or  chlorine  about  the  camera  or  other  apparatus  ; they 
possess  the  quality  of  effacing  the  effects  of  light,  and  the 
most  common  source  of  failure  among  Daguerreotype  artists 
is  due  to  neglecting  this  precaution. 

There  are  some  important  difficulties  to  which  the  Da- 
guerreotype is  liable.  For  taking  landscapes  it  is  not  avail- 
able. Green  and  red  colors  impress  no  change  upon  it. 
The  order  of  colors  and  light  and  shadow  is  not,  therefore, 
strictly  observed. 

There  are  many  other  photogenic  processes  now  known : 
several  have  been  invented  by  Mr.  Talbot ; among  them 
may  be  mentioned  the  calotype.  Sir  J.  Herschel,  also,  has 
discovered  very  beautiful  ones,  and  these  possess  the  great 
advantage  over  Daguerre’s,  that  they  yield  pictures  upon 
paper.  In  minuteness  of  effect  they  can  not,  however,  be 
compared  to  the  Daguerreotype. 


LECTURE  XXIV. 

The  Chemical  Action  op  Light. — Fixed  Lines. — Phos- 
phorescence.— Decomposition  of  Carbonic  Acid. — Spec- 
tral Impressions.  — Effects  of  Amplitude,  Frequency, 
and  Direction. — Cause  of  Chemical  Decompositions  by 
Light. 

The  fixed  lines  discovered  in  the  luminous  spectrum,  as 
represented  in  Fig.  63,  also  occur  in  the  impressions  left 
upon  sensitive  surfaces  on  which  the  spectrum  is  received. 


In  this  process,  is  iodine  set  free  from  the  plate  ? With  what  does  the 
iodine  unite  under  the  influence  of  the  mercurial  vapor?  Why  is  not  the 
Daguerreotype  applicable  to  landscapes  ? Mention  other  processes  of  pho- 
togenic drawing.  Can  the  fixed  lines  be  depicted  on  sensitive  surfaces  ? 


CHEMICAL  ACTION  OF  LIGHT. 


103 


as  was  discovered  by  M.  Becquerel  and  myself  about  the 
same  time  (1842).  In  this  instance,  however,  they  are  far 
more  numerous,  and  occur  in  groups  of  many  hundreds  be- 
yond the  visible  limits  of  the  violet  ray. 

It  has  already  been  mentioned  that  light  causes  the  phos- 
phorescence of  most  bodies.  Thus,  if  oyster-shells  be  cal- 
cined with  sulphur  and  exposed  to  the  sun,  they  shine  for  a 
considerable  time  after  in  the  dark.  Nor  does  it  require 
that  the  time  of  exposure  should  be  protracted ; the  flash 
of  an  electric  spark  is  sufficient  But,  what  is  very  remark- 
able in  this  case,  the  rays  which  excite  the  phosphorescence 
can  not  pass  through  a piece  of  colorless  glass ; to  them  it 
is  quite  opaque.  The  experiments  of  Mr.  Wilson  show  that 
a great  number  of  bodies  not  commonly  supposed  to  be  phos- 
phorescent are  so  in  reality ; that  for  a few  moments  after 
they  have  been  exposed  to  the  sun,  they  emit  a phosphores- 
cent light.  Thus  a sheet  of  writing  paper,  on  which  a key 
had  been  laid,  having  been  exposed  for  a few  moments  to 
the  sun,  on  being  suddenly  removed  to  a dark  room,  emitted 
a pale  light,  the  shadow  of  the  key  being  perfectly  visible. 
Even  the  hand,  after  being  dipped  in  the  sunshine,  emitted 
subsequently  light  enough  to'be  visible  in  a dark  place. 

The  various  principles  of  which  we  have  been  speaking 
exert  no  ordinary  control  over  the  phenomena  of  the  natural 
world.  Thus  it  is  to  the  influence  of  light  that  the  vegeta- 
ble world,  owes  its  existence ; for  plants  can  only  obtain 
carbon  from  the  air  while  the  sun  is  shining  on  them,  and 
it  is  of  that  carbon  that  their  solid  structures  are  chiefly 
formed.  It  has  been  a question  to  which  ray  this  eflect  is 
due  ; but  in  1843  I prov-^  that  it  is  the  yellow  light  which 
is  involved.  Dr.  Priestley  discovered  that  the  leaves  of 
plants  will  effect  the  decomposition  of  carbonic  acid  gas  un- 
der water ; and  on  immersing  tubes  filled  with  water  hold- 
ing this  gas  in  solution,  and  containing  a few  green  leaves, 
I found  that  at  the  blue  extremity  of  the  spectrum  no  effect 
whatever  took  place,  while  decomposition  went  on  rapidly 
in  the  yellow  ray. 

As  connected  with  the  minute  changes  of  surface  which 
are  effected  when  the  different  radiant  principles  fall  upon 
foodies,  as  in  the  instance  of  the  Daguerreotype,  we  may 
here  allude  to  the  formation  of  spectral  impressions,  which, 

What  is  Mr.  Wilson’s  experiment  ? What  ray  effects  the  decomposition 
of  carbonic  acid  ? What  are  spectral  impressions  ? 


104 


CHEMICAL  ACTION  OP  LIGHT. 


though  invisible,  may  be  brought  out  by  proper  processes. 
One  of  these  I described  several  years  ago.  Take  a piece 
of  polished  metal,  glass,  or  japanned  tin,  the  temperature  of 
which  is  low,  and,  having  laid  upon  it  a wafer,  coin,  or  any 
other  such  object,  breathe  upon  the  surface  ; allow  the  breath 
entirely  to  disappear  ; then  toss  the  object  off  the  surface  and 
examine  it  minutely  ; no  trace  of  any  thing  is  visible,  yet  a 
spectral  impression  exists  on  that  surface,  which  may  be 
evoked  by  breathing  upon  it.  A form  resembling  the  object 
at  once  appears,  and,  what  is  very  remarkable,  it  may  be 
called  forth  many  times  in  succession,  and  even  at  the  end 
of  many  months.  Other  instances  of  the  kind  have  subse- 
quently been  described  by  M.  Moser. 

On  the  Chemical  Action  of  Light. 

In  considering  the  action  of  a ray  of  light  upon  a decom- 
posable body,  there  artf  three  different  points  to  be  discussed, 
so  far  as  the  ray  itself  is  concerned : 1st.  To  what  extent, 
and  in  what  manner,  is  the  result  affected  by  the  intensity 
of  the  ray ; i.e.^  by  the  amplitude  of  the  vibrating  excur- 
sions ? 2d.  How  is  it  affected  by  Xhe  frequency  of  the  pul- 
satory impressions  ? 3d.  How  by  the  direction  in  which 

the  vibrations  are  made,  as  involved  in  the  idea  of  polariza- 
tion? 

1st.  By  means  of  burning  lenses  I found  that  it  is  not  the 
intensity  of  a beam  which  determines  its  decomposing  pow- 
er, and  that  we  can  not  produce  greater  effects  by  concen- 
trated light  than  we  can  by  the  application  of  the  simple 
sunbeam  continued  for  an  equivalent  period  of  time.  Nor 
can  such  optical  contrivances  effect  the  decomposition  of  sub- 
stances on  which  a feeble  beam  has  no  action. 

2d.  Rays  of  the  highest  refrangibility,  and,  therefore,  of 
the  most  frequent  vibrations,  commonly  have  the  greatest 
activity.  On  the  number  of  impulses  a ray  can  communi- 
cate in  a given  period  of  time,  depends  its  power  of  destroy- 
ing the  constitution  of  any  group  of  atoms.  And  the  phe- 
nomena of  interference  arising  from  the  superposition  of 
wave  motions  occur  exactly  as  might  have  been  predicted. 

3d.  The  direction  of  wave  motion  as  involved  in  the  idea 
of  polarization,  whether  plane  or  circular,  seems  to  exert  no 
effect. 

How  far  does  the  chemical  action  of  a ray  depend  on  amplitude  ? How 
far  on  w ave-length  or  frequency  ? How  far  on  the  polarized  condition  ? 


ELECTRICAL  MACHINES. 


105 


The  immediate  cause  of  the  decomposition  of  substances 
by  the  agency  of  light  is,  that  the  rays  forcing  the  material 
particles  on  which  they  fall  into  a state  of  rapid  vibration, 
in  many  compound  molecules  the  constituent  atoms  can  no 
longer  exist  together  as  the  same  group,  because  of  the  im- 
possibility of  their  being  animated  by  conspiring  motions,  and 
dislocation,  rearrangement,  or  decomposition  is  the  result. 


LECTURE  XXV. 

Electricity. — First  Observations  in  Electricity. — De- 
scription of  Electrical  Machines. — The  Spark  a Test 
of  Electrical  Excitement.  — Repulsion  of  Electrified 
Bodies. — Simple  Means  of  Excitement. — Conductoi'S 
and  Non-conductors.  — Insulation.  — Electric  Effects 
take  place  through  Glass. — Medicated  Tubes. 

It  was  observed,  six  hundred  years  before  Christ,  that  a 
piece  of  amber,  when  rubbed,  acquired  the  quality  of  attract- 
ing light  bodies.  This  fact  remained  without  value  for  more 
than  two  thousand  years,  a striking  memorial  of  the  barren 
nature  of  the  philosophy  of  those  times.  Within  the  last 
two  hundred  years  it  has  given  birth  to  an  entire  group  of 
sciences,  and  established  the  existence  of  an  imponderable 
principle,  which,  from  the  Greek  word  TjXsKTpov,  signifying 
amber,  has  taken  the  name  Electricity. 

The  catalogue  of  substances  in  Fig.  75. 

which  electric  development  can  be 
produced  was  greatly  increased  by 
Gilbert,  who  showed  that  glass, 
resin,  wax,  and  many  other  bodies 
are  equally  effective  as  amber.  To 
his  successors  we  owe  the  electrical 
machine,  an  instrument  which  en- 
ables us  readily  to  demonstrate  the 
properties  of  electricity. 

Electrical  machines  are  of  dif- 
ferent kinds.  They  may,  however, 
be  divided  into  plate  and  cylinder 

What  is  the  immediate  cause  of  decomposition  by  the  agency  of  light? 
What  was  the  first  observation  made  in  electricity?  From  what  does  the 
agent  derive  its  name  ? What  varieties  of  electrical  machines  have  we  ? 

E 2 


106  ELECTRICAL  MACHINES. 

machines.  These  instruments  are  respectively  represented^ 

inFig.75  3indFig.76.  In 
each  of  them  there  are  three 
distinct  portions.  First,  a 
piece  of  glass,  the  shape  of 
•which  differs  in  different  ca- 
ses; in  Fig.  75  it  is  a cir- 
cular plate,  in  Fig.  7 6 a cyl- 
inder; and  from  these  the 
instruments  take  their  name. 
Second,  the  rubbers,  made  of 
silk  or  leather,  stuffed  with 
hair  : the  office  of  these  is  to  press  lightly  on  the  glass  as  it 
turns  round,  and  produce  friction.  Third,  a brass  body,  of 
a cylindrical  or  rounded  shape,  but  with  points  on  that  por- 
tion of  it  which  looks  toward  the  glass.  It  is  supported  on 
glass  props,  and  is  termed  the  prime  conductor.  Some  mech- 
anism, such  as  a winch,  is  required  to  turn  the  glass  on  its 
axis ; and  when  it  is  desired  to  bring  the  machine  into  activity, 
all  the  parts  of  it  having  been  made  thoroughly  clean  and  dry 
by  rubbing  with  a piece  of  warm  silk  or  flannel,  a little  Mo- 
saic gold  or  amalgam  of  zinc  being  spread  on  the  rubber,  as 
soon  as  the  winch  is  turned  the  instrument  becomes  excited. 

One  of  the  most  striking  manifestations  of  electrical  de- 
velopment is  the  spark  ; this,  which  must  have  been  often 
seen  when  the  back  of  the  domestic  cat  is  rubbed  on  a frosty 
night,  was  discovered  in  the  case  of  glass  or  sulphur  by 
Otto  Guericke,  and  by  him  referred  to  its  proper  source, 
electric  excitement.  On  presenting  a brass  ball  or  the  fin- 
ger to  the  prime  conductor  of  the  machine,  the  spark  passes, 
attended  with  a slight  report.  It  may  be  very  beautifully 
Fie-  77-  shown  by  pasting  small  pieces  of  tin- 

foil  round  a glass  tube  in  a spiral 
a ^ c form,  as  shown  in  Fig.  77,  a h c, 

distances  of  the  twentieth  of  an  inch  intervening  between 
each  piece,  and  the  ends  of  the  tube  terminated  by  balls. 
On  presenting  one  of  these  balls  to  the  prime  conductor, 
and  holding  the  other  in  the  hand,  as  the  spark  passes,  it 
has  to  leap  over  each  interstice  between  the  spangles  of  tin- 
foil,  and  exhibits  a beautiful  spiral  line  of  light. 

What  are  the  three  essential  parts  of  these  machines  ? What  is  the  rub- 
ber ? What  is  the  prime  conductor  ? How  is  the  machine  excited  ? How 
may  the  electric  spark  be  exhibited  ? 


ELECTRICAL  LIGHT  AND  REPULSION. 


107 


Fig.  79. 


By  pasting  the  tin-foil  on  a pane  of  glass  in  such  a way 
as  to  direct  the  spark  properly, 
words  may  be  written  in  electric 
light,  as  shown  in  Fig.  78. 

As  the  electric  spark  can  hard- 
ly be  confounded  with  any  other 
physical  phenomenon  whatever,  its  presence  is  always  in- 
dubitable evidence  of  electric  excitement.  Thus  we  can 
prove  that  electricity  may  be  transferred  to  the  human  body 
from  the  machine,  by  placing  a man  on 
a stool  supported  by  glass  pillars.  Fig. 

79.  If  he  touches  the  prime  conductor  j 
with  one  hand,  sparks  may  be  drawn 
from  any  part  of  his  clothing  or  body. 

To  Otto  Guericke,  who  was  also  the 
inventor  of  the  air  pump,  we  owe  another  of  the  most  im- 
portant discoveries  in  electricity : that  bodies  qq 

which  have  touched  an  excited  substance  are 
subsequently  repelled  by  it ; thus,  if  we  rub  a 
glass  tube.  Fig.  80,  a,  until  it  becomes  electri- 
fied, and  then  present  it  to  a feather,  by  sus- 
pended by  a silk  thread  to  a stand,  c,  the  feather 
is  at  first  attracted,  and  then  immediately  re- 
pelled. 

On  this  principle,  that  under  certain  circum- ' 
stances  repulsion  takes  place,  are  founded  different  methods 
for  ascertaining  the  existence  of  electric  excite-  F>g.  8i. 
ment,  when  too  feeble  to  cause  a spark.  Thus 
two  light  balls  of  cork,  Fig.  81,  a b,  suspended 
by  linen  threads  so  as  to  hang  side  by  side,  as 
soon  as  they  are  electrified,  repel  each  other. 

It  does  not,  however,  require  an  electrical 
machine  to  demonstrate  the  principles  of  this 
agent.  A piece  of  stout  brown  paper  three  inches  wide, 
and  a foot  long,  if  held  before  the  fire  until  it  is  quite  dry  and 
smokes,  and  then  drawn  between  the  knee  and  the  sleeve, 
becomes  highly  excited,  especially  if  the  person  wears  wool- 
en clothing.  It  will  yield  sparks  more  than  an  inch  long. 

Let  a,  Fig.  82,  be  the  termination  of  the  prime  conduct- 

Why  may  it  be  used  as  a test  for  electric  excitement  ? Can  electricity 
be  transferred  from  the  machine  to  the  body?  What  discovery  did  Otto 
Guericke  make  in  electricity?  How  may  this  property  of  repulsion  be  il-* 
bistrated  ? By  what  simple  means  may  electrical  experiments  be  made  ? * 


n b 


108  CONDUCTORS  AND  NON-CONDUCTORS. 

Fig.  82.  or,  and  in  a hole  in  it  place  the  long 

h ^ brass  rod  h,  terminated  by  the  brass 

ball  c.  If  the  finger  is  approached  to 
the  ball,  sparks  freely  pass,  showing  that  along  brass  elec- 
tricity is  conducted  ; but  if  a glass  rod  of  the  same  diameter 
and  length,  and  terminated  by  a brass  ball,  be  employed, 

I not  a solitary  spark  can  be  obtained,  proving  that  glass  is  a 
non-conductor  of  electricity. 

|i^  The  important  fact  that  substances  may  be  divided  into 
two  classes,  conductors  and  non-conductors,  was  first  acci- 
dentally discovered  by  Dr.  Grey,  who  found  that  all  metals 
and  moist  bodies  are  conductors,  and  that  glass,  resins,  wax, 
sulphur,  atmospheric  air,  are  non-conductors.  In  the  treat- 
ises on  chemistry,  tables  may  be  found  exhibiting  the  rela- 
tions of  bodies  in  this  respect.  The  conducting  power  of 
the  same  substance  differs  with  circumstances ; thus  ice 
and  glass  are  non-conductors,  but  water  and  melted  glass 
are  conductors. 

"We  see,  from  these  facts,  the  explanation  of  the  structure 
of  the  prime  conductor ; the  electricity  derived  from  the  glass 
by  friction  passes  easily  along  the  brass  portion,  but  can  not 
escape  into  the  earth,  owing  to  the  glass  supports  which  re- 
fuse it  a passage.  When  a body  is  thus  placed  upon  glass, 
it  is  said  to  be  electrically  insulated,  and  the  process  is 
called  insulation. 

Although  electricity  can  not  pass  through  glass.  Sir  Isaac 
Newton  found  that  this  substance  is  no  impediment  to  the 
exertion  of  its  influences.  Thus,  in  Fig. 
83,  if  a be  the  brass  ball  of  the  prime 
conductor,  any  light  objects,  such  as  bits 
of  paper  or  fragments  of  cork,  placed  on  a 
metal  stand,  b,  beneath,  will  be  attracted  ; 
and  though  a pane  of  glass,  c,  be  placed 
between  a and  h,  still  the  same  phenom- 
enon takes  place.  . . 

Soon  after  electricity  became  a subject  of  popular  atten- 
tion, it  was  currently  believed  that,  if  medicines  of  various 
kinds  were  sealed  up  in  glass  tubes,  and  the  tubes  electri- 
cally excited,  their  peculiar  virtues  would  be  exhaled  in  such 


How  may  it  be  proved  that  brass  is  a conductor  and  glass  a non-conduct- 
or? Mention  some  of  the  leading  substances  belonging  to  each  of  these 
classes.  Explain  the  structure  of  the  prime  conductor.  Can  electric  influ- 
ences pass  through  glass  ? What  was' formed v meant  bv  medicated  tubes 


TWO  SPECIES  OP  ELECTRICITY. 


109 


a manneir  as  to  impress  the  operator  with  their  specific  ptsr- 
gative,  emetic,  or  other  powers.  Like  many  of  the  popular 
delusions  of  our  times,  this  imposture  was  supported  by  the 
most  cogent  evidence,  and  maladies  cured  publicly  all  over 
Europe.  Like  them,  these  “ medicated  tubes’"  have  served 
to  prove  the  worthlessness  of  human  testimony  when  de- 
rived from  the  prejudiced  and  ignorant. 

It  should  be  remarked  that,  in  their  action  upon  materiel 
bodies,  electricity  and  caloric  differ  greatly.  The  former  has 
no  kind  of  influence  in  determining  magnitude,  whereas  ths 
size  of  any  object  depends  upon  its  temperature. 


LECTURE  XXVI. 

Theory  of  Electrical  Induction. — Two  Species  of  Elec- 
tricity. — Their  Names.  — General  Law  of  Attraction 
and  Repulsion.  — Theory  of  IndiLction.  — Permanent 
Excitement  by  Induction. — Takes  place  through  Glass. 
— Illustrative  Experiments. 

A VERY  celebrated  French  electrician,  Dufay,  having 
caused  a light,  downy  feather  to  be  repelled  by -an  excited 
glass  tube,  intended  to  amuse  himself  by  chasing  it  round 
the  room  with  a piece  of  excited  sealing-wax.  To  his  sur- 
prise, instead  of  being  repelled,  the  feather  was  at  once  at- 
tracted. On  examining  the  cause  of  this  more  minutely,  he 
arrived  at  the  conclusion  that  there  are  two  species  of  elec- 
tricity, the  one  originating  when  glass  is  excited,  and*  the 
other  from  resin  or  wax.  To  these  he  gave  the  names  of 
vitreous  and  resinous  electricity,  thus  pointing  out  their  ori- 
gin ; they  are  also  called,  for  reasons  which  will  be  given 
hereafter,  positive  and  negative  electricities. 

He  found  that  these  different  electricities  possess  the  same 
general  physical  qualities  ; they  are  self-repulsive,  but  the 
one  is  attractive  of  the  other.  This  is  readily  proved  by 
hanging  a feather  by  a linen  thread  to  the  prime  conductor 
of  the  machine,  and,  when  it  is  excited,  bringing  near  to  it 


Does  electricity  affect  the  magnitude  of  bodies  ? How  was  it  first  dis 
covered  that  there  are  two  species  of  electricity  ? What  names  have  been 
given  to  these  electricities  ? What  are  their  physical  qualities  t How  may 
this  self-repulsion  and  mutual  attraction  be  proved  ? 


110 


ELECTRICAL  INDUCTION, 


an  excited  glass  tube.  The  feather  is  already  vitreously 
electrified,  and  the  tube,  being  in  the  same  condition,  at 
once  repels  it ; but  a stick  of  excited  sealing-wax  being  res- 
inously  electrified,  that  is  to  say,  in  the  opposite  condition 
to  the  feather,  at  once  attracts  it.  Two  cork  balls,  as  in 
Fig.  81,  suspended  by  conducting  threads,  always  repel  one 
another  when  both  are  excited  either  vitreously  or  resinous- 
ly ; but  if  one  be  vitreous  and  the  other  resinous,  they  attract. 

These  various  results  may  all  be  grouped  under  the  fol- 
lowing general  law,  which  includes  the  explanation  of  a 
great  many  electrical  phenomena.  Bodies  electrified  dis- 
similarly attract,  and  bodies  electrified  similarly  repel ; or, 
more  briefly,  like  electricities  repel,  and  unlike  ones  attract. 

There  are  many  ways  in  which  electrical  excitement  can 
be  developed  : in  the  common  machine  it  is  by  friction  ; in 
the  tourmaline,  a crystallized  gem,  by  heat ; and  in  other 
cases,  by  chemical  action  and  by  conduction.  Electrical  dis- 
turbance also  very  often  arises  from  induction. 

By  the  term  electrical  induction  we  mean  that  a body 
which  is  already  excited  tends  to  disturb  the  condition  of 
others  in  its  neighborhood,  inducing  in  them  an  electric  con- 
dition. 

Thus,  let  a.  Fig.  84,  be  the  terminal  ball  of  the  prime 
conductor,  and  a few  inches  ofl' 
p.  let  there  be  placed  a secondary 
conductor,  d c,  of  brass  supported 
^ on  a glass  stand,  and  at  each  ex- 
tremity, d and  c,  of  the  conduct- 
or, let  there  be  arranged  a pair 
of  cork  balls  suspended  by  linen 
threads,  as  shown  in  the  figure. 
As  soon  as  the  ball,  a,  is  electrified  by  turning  the  machine, 
and  without  any  spark  passing  from  it  to  the  secondary  con- 
ductor, the  balls  will  begin  to  diverge,  showing  that  the 
condition  of  that  conductor  is  disturbed  by  the  neighborhood 
of  the  excited  ball,  a. 

It  will  farther  be  found,  on  presenting  an  excited  piece 
of  sealing  wax  to  the  pairs  of  cork  balls,  that  one  set  is  at- 
tracted, and  the  other  repelled.  They  are,  therefore,  in  op- 


What  is  the  general  law  of  electric  attractions  and  repulsions  ^ In  what 
ways  may  electric  excitements  be  developed  ? What  is  the  meaning  of  elec- 
tric induction  ? Give  an  illustration.  In  a secondary  conductor  disturbed 
by  an  electrified  body,  what  are  the  conditions  of  its  ends  ? 


* & 


Fig.  84. 

h 


ELECTRICAL  INDUCTION. 


Ill 


Fig.  85. 


posite  electrical  states.  The  disturbing  ball  is  vitreously 
electrified,  and  that  end  of  the  secondary  conductor  nearest 
it  is  resinous,  the  farther  end  being  vitreous.  If  the  disturb- 
ing ball,  a,  be  no^v  removed,  the  electric  disturbance  ceases, 
and  the  corks  no  longer  diverge. 

These  phenomena  of  electric  induction  are  not  dependent 
on  the  shape  of  bodies^  Let  there  be  two  flat 
circular  plates,  a 5,  Fig.  85,  supported  on 
glass  stands,  and  set  a few  inches  apart,  look* 
ing  face  to  face.  Let  one  of  them,  be  elec- 
trified positively  by  contact  with  the  prime 
conductor,  as  indicated  by  the  sign  + ; it  im- 
mediately induces  a change  in  the  opposite 
plate,  the  nearest  face  of  which  becomes  neg- 
ative — , and  the  more  distant,  positive.  It  is  evident  that 
this  disturbance  is  a consequence  of  the  law,  that  “ like  elec- 
tricities repel,  and  unlike  ones  attract.’*  In  the  plate  5,  both 
species  of  electricity  exist,  and  a being  made  positive,  even 
though  at  a distance,  exerts  its  attractive  and  repulsive  agen- 
cies on  the  electric  fluid  of  5,  the  negative  electricity  of 
which  it  attracts,  and  draws  near  to  it ; the  positive  it  re- 
pels and  drives  to  the  farthest  side  ; so  that  the  disturbed 
condition  of  the  body  5 is  a result  of  the  fact,  that  a being 
electrified  positively,  will  repel  positive  electricity  and  at- 
tract negative. 

Now  let  the  plate  h be  touched  by  the  finger,  or  a chan- 
nel of  communication  opened  with  the  earth ; the  positive 
electricity  of  a still  exerting  its  repulsive  agency  on  that  of 
5,  will  drive  it  into  the  ground,  and  h will  now  become  neg- 
ative all  over. 

Let  h be  once  more  insulated  by  breaking  its  communi- 
cation with  the  ground,  and  let  a be  removed  ; it  will  now 
be  found  that  h is  permanently  electrified,  and  in  the  oppo- 
site condition  to  a.  -pig.  86. 

By  manipulating  in  this  manner,  we  can  there- 
fore effect  a permanent  disturbance  in  the  condi- 
tion of  an  insulated  body,  by  bringing  an  excited  \ 
one  in  its  neighborhood. 

In  these  changes,  the  intervention  of  a piece 
of  glass  makes  no  difference.  Let  a circular  plate 
of  glass,  a,  Fig.  86,  be  set  so  as  to  intervene  be- 

What  is  the  cause  of  this  disturbance  ? How  may  we  by  induction  perma- 
nently electrify  a body  ? Can  electrical  induction  take  place  through  glass  ? 


112 


MISCELLANEOUS  EXPERIMENTS. 


Fig,  87. 


tween  the  metallic  plates,  a and  5,  and  still  all  the  phe- 
nomena occur  as  before.  Electric  induction,  therefore,  can 
take  place  through  glass. 

On  the  principles  of  induction,  and  of  electric  attraction 
and  repulsion,  many  very  interesting  experiments 
may  be  explained.  The  following  may  serve  as 
examples  : To  the  ball  of  the  prime  conductor,  Fig, 
S7,  let  there  be  suspended  a circular  plate  of  brass, 
«,  six  inches  in  diameter,  horizontally,  and  beneath 
) it  another  plate,  b,  supported  on  a conducting  foot, 
parallel  and  at  a distance  of  three  or  four  inches. 
On  the  lower  plate,  b,  place  slips  of  paper  or  of  other 
light  substance,  cut  into  the  figure  of  men  or  ani- 
mals. On  setting  the  machine  in  motion,  so  as  to 
electrify  the  upper  plate,  the  objects  move  up  and  down 
wdth  a dancing  motion  ; and  the  cause  is  obvious  : the  plate 
a being  positive,  repels  by  induction  the  positive  electricity 
of  the  figures  through  the  conducting  stand  into  the  earth, 
and  thus,  they  being  rendered  negative,  are  attracted  by  the 
upper  plate  ; on  touching  it,  they  become  electrified  posi- 
tively like  it,  and  then  are  repelled,  and  fall  down  to  dis- 
Fig  88  charge  their  electricity  into  the  ground, 

and  this  motion  is  continually  repeated. 

Upon  a horizontal  brass  bar,  a b,  Fig. 
88,  three  bells  are  suspended,  the  outer 
ones  at  a and  b by  chains,  the  middle 
one  at  c by  a silk  thread.  Between  the 
bells,  the  metallic  clappers,  cl  e,  are  sus- 
pended  by  silk,  and  from  the  center  bell 
the  chain y*  extends  to  the  table.  On  hanging  the  arrange- 
ment by  the  hook  at  g to  the  prime  conductor,  the  bells 
Fig.  89.  ring,  the  clappers  moving  from  the 

outer  to  the  Central  bell  and  back, 
alternately  striking  them. 

On  a pivot,  a.  Fig.  89,  suspend 
a bell  jar  having  four  pieces  of  tin- 
foil  pasted  on  its  sides,  bed;  con- 
nect the  jar,  by  means  of  the  insu- 
lated wire  3/,  with  the  prime  con- 
ductor, so  that  the  pieces  of  tin-foil 


Describe  the  experiment  of  the  dancing  figures,  and  explain  the  principles 
involved  in  it.  Describe  the  experiment  of  the  bells,  and  the  cause  of  their 
ringing.  Explain  the  arrangement  and  cause  of  movement  of  the  rotating  jar. 


113 


DISTRIBUTION  OF  ELECTRICITY. 

may  receive  sparks.  On  the  opposite  side  arrange  a con- 
ductor, X,  in  connection  with  the  ground  by  a chain.  On 
putting  the  machine  into  activity,  the  jar  will  commence 
rotating  on  its  pivot. 

Take  a cake  of  sealing  wax  or  gum  lac,  eight  or  ten 
inches  in  diameter,  and  receive  on  its  surface  a few  sparks 
from  the  prime  conductor  by  bringing  it  near  the  ball.  Then 
blow  upon  its  surface  from  a small  pair  of  bellows  a mix- 
ture of  flour  of  sulphur  and  red  lead,  which  have  been  in- 
timately ground  together  in  a mortar.  This  mixture  is  of 
an  orange  color,  but  the  moment  it  impinges  on  the  cake  it 
is,  as  it  were,  decomposed ; the  yellow  sulphur  settling  on 
one  portion,  and  the  red  lead  on  another,  giving  rise  to  very 
curious  and  fantastical  figures. 


LECTURE  XXVII. 

Laws  of  the  Distribution  of  Electricity,  and  the  Gen- 
eral Theories. — Distribution  of  Electricity. — On  a 
Sphere.  — Ellipsoid. — Action  of  Points.  — Franklin's 
Discovery  of  the  Identity  of  Electricity  and  Lightning. 
— Tlbe  Leyden  Jar. — The  Discharging  Rod. — The 
Electric  Battery. 

When  electricity  is  communicated  to  a conducting  body, 
it  does  not  distribute  itself  uniformly  through  the  whole  mass, 
but  exclusively  upon  the  surface  ; thus,  if  to  the  spherical 
ball  a,  Fig.  90,  supported  on  an  in-  Fig.^o. 

sulating  foot,  b,  there  be  adjusted  two 
hemispherical  caps,  c c,  also  on  insu- 
lating handles,  it  may  be  proved  that 
any  electricity  communicated  to  a dis- 
tributes itself  entirely  on  its  surface  ; 
for  if  we  place  upon  a the  caps  c c, 
and  then  remove  them,  it  will  be  found  that  every  trace 
of  electricity  has  disappeared  from  a,  and  has  accumulated 
on  the  caps,  which,  while  they  were  upon  the  ball,  formed 
its  superficies. 

How  may  p©wder  of  sulphur  and  red  lead  mixed  together  be  separated  ? 
Does  electricity  distribute  itself  on  the  surface  or  m the  interior  of  bodies  t 
How  may  its  superficial  distribution  be  pioved  ? 


114 


DISTRIBUTION  OF  ELECTRICITY. 


Fig.  92. 


Again,  if  we  take  a large  brass  ball,  a,  Fig.  91, 
supported  on  an  insulating  stand,  and  having  on  its 
upper  portion  an  aperture,  through  which  we  may 
have  access  to  its  interior,  it  will  be  found,  on  ex- 
amination, that  the  most  delicate  electrometers  can 
discover  no  electricity  within  the  ball,  the  whole  of 
it  being  on  the  external  superficies. 

In  the  case  of  a spherical  body,  not  only  is  the 
distribution  entirely  superficial,  but  it  is  also  uni- 
form ; each  portion  of  the  sphere  is  electrified  alike.  But 
where,  instead  of  a spherical,  we  have  an  ellipsoidal  body, 
it  is  different ; thus,  if  we  examine  the  condition  of  such  a 
conductor,  Fig.  92,  the  quantity  of  elec- 
tricity in  its  middle  portion,  as  at  a,  will 
be  the  smallest,  and  it  increases  as  we 
advance  toward  the  ends,  b and  c ; and 
in  different  ellipsoids,  as  the  length  be- 
comes greater,  so  the  amount  of  elec- 
tricity found  on  the  extremities  is  great- 
er. When,  therefore,  a conductor  of  an 
oblong  spheroidal  shape  is  used,  the  in- 
tensity of  electricity  at  the  extremities  of  the  two  axes,  a d 
and  b c,  Fig.  92,  is  exactly  in  the  proportion  of  the  length 
of  those  axes  themselves  ; and  should  the  disproportion  in 
length  and  breadth  of  the  conducting  body  be  very  great, 
as  in  the  case  of  a long  wire  or  other  pointed  body,  a very 
great  concentration  will  take  place  upon  the  points.  On 
this  principle  we  explain  the  efiect  of  pointed  bodies  on  con- 
ductors : if  the  prime  conductor  of  the  machine  have  a nee- 
dle or  pin  fixed  upon  it,  the  electricity  escapes  away  into  the 
air,  visibly  in  a dark  room ; and  in  the  same  way,  if  pointed 
bodies  surround  the  electrical  machine,  it  can  not  be  highly 
excited,  as  they  rapidly  take  the  charge  from  its  conductor. 

At  a very  early  period  electricians  had  observed  the  close 
similarity  between  the  phenomena  of  the  electric  spark  and 
those  of  lightning,  but  in  the  year  1752  Dr.  Franklin  proved 
that  they  were  identical.  He  was  waiting  for  the  erection 
of  the  spire  of  a church  in  Philadelphia,  on  the  extremity 
of  which  he  intended  to  raise  a pointed  metal  rod,  with  a 


In  the  interior  of  an  electrified  hollow  ball,  does  any  electricity  exist  ? 
On  a spherical  body,  is  the  distribution  uniform  ? How  is  it  on  an  ellipsoid? 
When  the  disproportion  of  the  axes  of  the  ellipsoid  is  great,  what  is  the  dis- 
tribution ? How  may  we  explain  the  effect  of  pointed  bodies  ? 


THEORIES  OF  ELECTRICITY. 


115 


view  of  withdrawing  the  electricity  from  the  clouds,  when 
the  accidental  sight  of  a boy’s  kite  suggest  d to  him  that 
ready  means  of  obtaining  access  to  the  more  elevated  re- 
gions of  the  air.  Accordingly,  having  stretched  a silk  hand- 
kerchief over  a light  wooden  cross,  and  arranged  it  as  a kite, 
he  attached  to  it  a hempen  string  terminating  in  a silk  cord, 
and,  taking  advantage  of  a thunder  storm,  raised  it  in  the 
air ; for  a time  no  result  was  obtained,  but  the  string  be- 
coming wet  by  the  rain,  and  thereby  rendered  a better  con- 
ductor, he  perceived  the  filaments  which  hung  upon  it  re- 
pelling one  another,  and  on  presenting  his  knuckle  to  a key 
which  had  been  tied  to  the  end  of  the  hempen  string,  re- 
ceived an  electric  spark.  The  identity  of  lightning  and 
electricity  was  proved. 

Franklin  soon  made  a useful  application  of  his  discovery ; 
he  proposed  to  protect  buildings  from  the  effects  of  lightning 
by  furnishing  them  with  a metallic  rod,  pointed  at  its  upper 
extremity,  and  projecting  some  feet  above  the  highest  part 
of  the  building,  and  continuously  extending  downward  until 
it  was  deeply  buried  in  the  ground.  This  contrivance,  the 
lightning  rod,  is  now,  as  is  well  known,  extensively  applied. 

There  are  two  theories  respecting  the  nature  of  electric- 
ity : 1st,  Franklin’s  theory,  which  assumes  that  there  is  but 
one  fluid ; 2d,  the  theory  of  two  fluids,  called  also  Dufay’s 
theory. 

Franklin’s  theory  is,  that  there  exists  throughout  all  space 
a subtle  and  exceedingly  elastic  fluid,  called  the  electric 
fluid,  the  peculiarity  of  which  is,  that  it  is  repulsive  of  its 
own  particles,  but  attractive  of  the  particles  of  other  mat- 
ter ; that  there  is  a specific  quantity  of  this  fluid  which 
bodies  arc  disposed  to  assume  when  in  a natural  condition 
or  state  of  equilibrium  ; and  that,  if  we  communicate  to 
them  more  than  their  natural  quantity,  they  become  posi- 
tively electrified ; or,  if  we  take  from  a portion  of  that  which 
is  natural  to  them,  they  become  negatively  electrified. 

Dufay’s  theory  is,  that  there  exists  throughout  all  space 
a universal  medium,  called  the  electric  fluid,  of  which  the 
immediate  properties  are  unknown,  but  which  is  composed 
of  two  species  or  varieties  of  electricity,  the  vitreous  and 

Under  what  circumstances  was  the  discovery  of  the  identity  of  lightning 
and  electricity  made?  What  is  the  lightning  rod  ? What  theories  of  elec- 
tricity have  been  introduced  ? What  is  Franklin’s  theory  ? What  is  the 
theory  of  Dufay  ? 


116 


THE  LEYDEN  JAR. 


resinous,  called  also  the  positive  and  negative ; that,  as  re-" 
spects  itself,  each  of  these  electricities  is  repulsive,  hut  at- 
tractive of  the  other  kind  ; and  that,  when  they  coexist  in 
equal  quantities  in  a body,  it  is  in  a neutral  state  or  condi- 
tion of  equilibrium,  but  if  the  positive  or  negative  electrici- 
ties are  in  excess,  it  is  accordingly  positively  or  negatively 
electrified. 

In  some  respects  the  theory  of  two  electricities  ha^  ad- 
vantages over  that  of  one  ; by  it  several  phenomena  can  be 
explained  which  are  difficult  of  explanation  by  the  other. 
Among  such  may  be  mentioned  the  repulsion  of  negatively 
electrified  bodies,  and  the  distribution  of  negative  electricity 
on  the  surface  of  conductors,  which  is  the  same  as  that  of 
positive. 

On  the  principles  of  either  of  these  theories,  we  can  see 
how  it  is  that  we  can  never  produce  one  kind  of  electricity 
without  the  other  simultaneously  appearing.  In  the  com- 
mon electrical  machine,  if  the  revolving  glass  is  positively 
electrified,  the  rubbers  which  produce  the  friction  are  nega- 
tive ; in  the  tourmaline,  if  one  end  of  the  crystal,  when 
warmed,  becomes  positive,  the  other  end  is  negative.  The 
two  varieties  must  be  always  co-ordinately  generated.  “ 

In  1745  the  Leyden  jar  was  discovered.  This  consists  of 
Fig,  93.  a glass  jar,  Fig.  93,  coated  on  its  inside  with 

C a piece  of  tin-foil  within  an  inch  or  two  of  its 

upper  edge,  and  also  on  its  outside  to  the  same 
point ; through  the  cork  which  closes  the  mouth 
of  the  jar,  a brass  rod,  terminated  by  a ball, 
BB|||  I passes  ; the  rod  reaches  down  to  the  inside 
BBII  i coating  and  touches  it.  On  holding  this  instru- 
-JHBII  IL  exterior  coating,  and  presenting 

H|n|  its  ball  to  the  prime  conductor,  a torrent  of 
sparks  passes  into  the  jar  : and  when  it  is  fully 
charged,  if,  still  retaining  one  hand  in  contact  with  the  out- 
side, we  touch  the  ball,  a bright  spark  passes,  with  a loud 
snapping  noise,  and  the  operator  receives  through  his  arms 
and  breast  what  is  called  the  electric  shock. 

If  we  take  the  discharging  rod,  Fig.  94,  consisting  of  two 
brass  arms,  a a,  terminated  by  balls  working  on  a joint,  b, 


In  what  points  does  the  latter  appear  to  be  more  correct  than  the  former  ? 
Why  are  twth  electricities  always  produced  together  ? Describe  the  struc- 
ture of  the  Leyden  jar.  How  may  it  be  used?  Describe  the  discharging 
rod. 


ELECTRIC  BATTERY. 


117 


and  supported  by  an  insulating  handle,  c,  by  bringing  one  of 
its  balls  in  contact  with  the  outside  coating  of  a Ley- 
den  jar,  and  its  other  ball  with  the  ball  of  the  jar,  ^ ^ 
the  discharge  will  take  place  as  before,  but  the  op- 
erator,  protected  by  the  glass  handle,  receives  no  V / 
shock. 

If  between  the  outside  coating  of  a jar  and  one  of  ^ 
the  balls  of  the  discharging  rod  a piece  of  card-board  ft 
is  made  to  intervene,  and  the  spark  passed,  the  card  TTc 
will  be  found  to  be  perforated,  a burr  being  raised  on  11 
both  sides  of  it,  as  though  two  threads  had  been  drawn  I j 
through  the  hole  in  opposite  directions  at  the  same  ^ 
time  ; and  from  this  an  argument  in  favor  of  the  theory  of 
two  fluids  has  been  drawn. 

When  a great  number  of  jars 
are  connected  together,  so  that  all 
their  inside  coatings  unite,  and  all 
their  outside  coatings  are  also  in 
contact,  they  constitute  what  is 
termed  an  electric  battery,  as  seen 
in  Fig.  95.  By  this  instrument 
many  of  the  more  violent  effects  of 
electricity  may  be  illustrated,  such 
as  the  splitting  of  pieces  of  wood, 
and  the  ignition  and  dispersion  of 
metallic  wires. 


LECTURE  XXVIII. 

ELECTFaCAL  INSTRUMENTS  AND  FaFvADAY’s  ThEORY  OF 
Electric  Polarization. — Theory  of  the  Leyden  Jar. 
— Quadrant.,  Gold-leaf  and  Torsion  Flectrometers. — 
Theory  of  Electric  Folarization.  — Specific  Inductive 
Capacity. 

The  office  which  is  discharged  by  the  metallic  coatings 
of  a Leyden  jar  is  illustrated  by  the  apparatus,  Fig.  96. 
It  consists  of  a conical  glass  jar,  to  the  interior  and  exterior 


How  is  it  used  ? What  is  the  effect  when  the  discharge  is  passed  through 
a piece  of  card-board?  Describe  the  electric  battery.  ^What  is  the  office 
of  the  coatings  of  the  Leydeii  jar  1 


118 


CONDENSING  ACTION* 


of  which  movable  coatings  of  thick  tin  plate  are  adapted, 
the  interior  one  having  a rod  and  ball  projecting 
from  it.  This  may  be  charged  like  any  other 
Leyden  vial,  but  on  taking  off  its  outside  coating 
and  removing  its  interior,  they  may  be  handled 
and  brought  in  contact  with  each  other,  and  no 
spark  passes ; but  on  restoring  them  to  their  for- 
mer position,  and  applying  the  discharging  rod,  the 
jar  is  discharged.  They  therefore  only  serve  to 
make  a complete  conducting  communication  be- 
tween all  parts  on  the  interior  and  all  on  the  exterior  of  the 
jar. 

The  condensing  action  of  the  Leyden  vial,  which  enables 
it  to  hold  so  large  a quantity  of  electricity,  is  due  to  induc- 
tion. When  the  inner  coating  is  brought  in  contact  with 
the  prime  conductor,  it  participates  in  its  electrical  condition. 
We  may  therefore  suppose  it  to  be  positively  electrified. 
The  positive  electricity  of  the  interior,  decomposing  the  elec- 
tric fluid  of  the  outside  coating,  repels  its  positive  electricity 
into  the  earth ; for  to  charge  a Leyden  vial  the  outside 
coating  is  placed  in  communication  with  the  ground.  It 
therefore  appears  that  the  inner  coating  is  positive,  the  outer 
negative,  and  the  whole  jar,  viewed  together,  is  in  the  neu- 
tral condition.  The  interior  coating  continues,  under  these 
circumstances,  to  receive  a farther  charge  from  the  prime 
conductor  ; by  induction  through  the  glass,  this  again  repels 
more  of  the  same  kind,  the  positive,  into  the  ground,  and  the 
negative  accumulates  as  before.  In  this  manner  an  indef- 
inite quantity  might  be  accumulated,  were  it  not  for  the  fact 
that,  owing  to  the  distance  which  intervenes  between  the 
two  coatings,  by  reason  of  the  thickness  of  the  glass,  the 
quantity  of  positive  electricity  in  the  interior  is  never  pre- 
cisely neutralized  by  the  quantity  of  negative  on  the  exte- 
rior, for  all  inductive  actions  enfeeble  as  the  distance  in- 
creases. 

The  action  of  the  Leyden  vial  may  be  illustrated  by  the 
following  experiments  : within  an  inch  of  the  ball,  a,  of 
the  prime  conductor,  Fig.  97,  bring  a secondary  conductor, 
5,  supported  on  an  insulating  stem,  c,  and  on  putting  the 

How  may  this  be  proved  ? To  what  cause  is  the  condensing  action  of 
the  Leyden  jar  due  ? What  is  the  action  of  the  positive  electricity  depos- 
ited on  the  inner  coating,  on  the  electric  fluid  of  the  outer  ? Why  must  the 
outer  coating  be  in  connection  with  the  ground  ^ Why  is  the  charge  of  the 
jar  limited  ? 


Fig.  96. 


ACTION  OF  THE  LEYDEN  JAR. 


119 


electrical  machine  in  activity,  two  or 
three  sparks  will  pass  from  a to  6,  ^ ^ 

but  after  that  no  more.  The  cause  ^ ^ 
of  the  refusal,  on  the  part  of  the  sec- 
ondary conductor,  to  receive  any  far- 
ther charge,  is  obviously  due  to  the 
fact  that  the  electricity  which  is  al- 
ready communicated  to  it  repels  that  upon  the  ball,  a,  and 
prevents  the  passage  of  any  more. 

If  now  we  take  a Leyden  jar  h.  Fig.  98,  and,  having  in- 
sulated it  on  a stand,  bring  it  within  a short  Fig.  98. 
distance  of  the  ball,  of  the  prime  con-  a 
ductor,  it  in  the  same  manner  will  only  re- 
ceive a few  sparks.  But  if  we  place  a 
conductor,  c,  which  is  connected  with  the 
ground,  near  to  the  outside  coating,  it  will 
be  found  that  for  every  spark  that  passes 
between  a and  b,  one  passes  between  the 
outside  coating  and  c,  and  the  sparks  follow 
each  other  in  rapid  succession,  until  the  jar 
becomes  fully  charged.  From  this,  therefore,  we  gather, 
that  while  positive  electricity  is  passing  into  the  interior  of 
the  jar,  it  is  escaping  from  the  exterior,  and  that  the  reason 
the  jar  condenses  is  because  its  sides  are  in  opposite  condi- 
tions, the  positive  electricity  of  the  interior  being  nearly 
neutralized  by  the  negative  electricity  of  the  exterior. 

Electrometers  are  instruments  for  measuring  the  99 
intensity  of  electric  excitement.  The  cork  balls, 
which  were  represented  in  Fig.  81,  are  one  of  the 
most  simple  of  these  contrivances.  The  distance  to 
which  they  will  diverge  is  a rough  measure  of  the 
intensity  of  the  electric  force.  The  quadrant  elec- 
trometer depends  essentially  on  the  same  principles. 

It  consists  of  an  upright  stem  of  wood.  Fig.  99,  to 
which  is  affixed  a semicircular  piece  of  ivory,  from 
the  centre  of  which  there  hangs  a light  cork  ball 
playing  upon  a pivot.  When  this  instrument  is 
placed  on  the  prime  conductor  or  other  electrified  body,  the 
stem  participates  in  the  electricity,  and,  repelling  the  cork 

What  is  the  reason  that  a secondary  insulated  conductor  refuses  to  re- 
ceive more  than  two  or  three  sparks?  When  the  Leyden  jar  is  insulated, 
can  it  be  charged  ? On  bringing  a conductor  in  connection  with  the  ground, 
near  the  outer  coating,  what  is  the  result  ? Describe  the  cork  ball  elec- 
trv)meter.  Describe  the  quadrant  electrometer. 


120 


ELECTROMETERS. 


ball  which  hangs  in  contact  with  it,  the  amount  of  repulsion 
may  be  read  off  on  the  graduated  semicircle ; but  it  is  ob- 
vious that  the  number  of  degrees  is  not  expressive  of  the 
true  electrical  intensity,  and  that  no  force,  no  matter  what 
its  intensity  may  be,  can  ever  repel  the  ball  beyond  ninety 
degrees. 

The  gold-leaf  eiectrometer.  Fig.  100, 
^ consists  of  a glass  cylinder,  a,  in  which  two 

gold  leaves  are  suspended  from  a conduct- 
ing rod  terminated  by  a ball  or  plate,  h. 
On  the  glass  opposite  the  leaves  pieces  of 
tin-foil  are  pasted,  so  that  when  the  leaves 
diverge  fully  they  may  discharge  their  elec- 
' tricity  into  the  ground.  This  is  a very  del- 
rr..—  icate  instrument  for  discovering  the  pres- 
ence of  electricity,  but  the  torsion  electrometer  of  Coulomb  is 
to  be  preferred  when  it  is  required  to  have  exact  measures 
of  the  quantity.  \ ^ 

Coulomb’s  electrometer  consists  of  a glass  cylinder,  a, 
Fig.  101,  upon  the  top  of  which  there  is 
fixed  a tube,  d,  in  the  axis  of  which  hangs 
a glass  thread,  h a,  to  the  lower  end  of 
which  a small  bar  of  gum  lac,  c,  with  a 
gilt  pith  ball  at  each  extremity,  is  fasten- 
ed. Through  an  aperture  in  the  top  of  the 
glass  cylinder,  another  gum  lac  rod,  d,  with 
gilt  balls,  may  be  introduced.  This  goes 
under  the  name  of  the  carrier  rod. 

If  now  the  lower  ball  of  the  carrier  rod 
be  charged  with  the  electricity  to  be  meas- 
ured, and  introduced  into  the  interior  of  the 
cylinder,  as  seen  in  the  figure,  it  will  repel 
the  movable  ball.  By  taking  hold  of  the 
button,  h,  to  which  the  upper  end  of  the 
glass  thread,  a,  is  attached,  we  may,  by  twisting  the  glass 
thread  forcibly,  bring  the  carrier  ball  and  the  movable  ballj 
in  contact.  The  number  of  degrees  through  which  the 
thread  requires  to  be  twisted  represents  the  amount  of  elec- 
tricity. To  the  button,  h,  an  index  and  scale  are  attached, 
not  shown  in  the  figure.  By  this  we  can  tell  the  numbei’ 
of  degrees  of  twist  or  torsion  which  have  been  given  to  the 

Why  does  the  quadrant  electrometer  give  inaccurate  indications  ? De-J 
scribe  the  gold  leaf  electrometer.  Describe  Coulomb’s  torsion  electrometer! 


FARADAY  S THEORY  OF  INDUCTION. 


121 


thread.  These  angles  of  torsion  are  exactly  proportional  to 
the  quantities  of  electricity. 

One  of  the  most  delicate  electroscopes  is  that  of  Bohnen, 
berger.  It  consists  of  a small  Zamboni’s 
pile,  a b,  Fig.  102,  supported  horizontally 
beneath  a glass  shade,  and  from  its  extremi- 
ties, a b,  curved  wires  pass,  which  terminate 
in  parallel  plates,  2^  One  of  these  is 

therefore  the  positive,  and  the  other  the  neg- 
ative pole  of  the  pile.  Between  them  there 
hangs  a gold  leaf,  d g,  which  is  in  metallic 
communication  with  the  plate  0 n by  means 
of  the  rod  c.  If  the  leaf  hangs  equally  be- 
tween the  two  plates,  it  is  equally  attracted  by  each,  and 
remains  motionless ; but,  on  communicating  the  lightest 
trace  of  electricity  to  the  plate  o 7i,  the  gold  leaf  instantly 
moves  toward  the  plate  which  has  the  opposite  polarity. 

Many  of  the  fundamental  phenomena  oT  electricity  have 
been  explained  by  Dr.  Faraday  upon  the  hypothesis  that  in- 
duction is  an  action  of  polarization,  taking  place  in  the  con- 
tiguous molecules  of  non-conducting  media,  and  propagated 
in  curved  lines. 

Whatever  may  be  the  form  or  constitution  of  bodies,  an 
electric  charge  can  not  be  given  to  them  without  at  the 
same  time  giving  a charge  of  the  opposite  kind,  but  of  the 
same  amount,  to  them  or  other  bodies  in  their  vicinity. 
This  charge  is  not  confined  upon  their  surfaces  by  the  press- 
ure of  the  atmosphere,  but  through  the  polarization  of  the 
aerial  or  solid  particles  of  the  surrounding  dielectrics,  pro- 
ducing in  them  a charge  of  the  same  amount,  but  of  an  op- 
posite kind.  Thus,  if  a positively  electrified  ball  be  placed 
ill  the  centre  of  a hollow  metallic  sphere,  the  intervening 
space  being  filled  with  atmospheric  air,  the  charge  is  not 
retained  upon  the  ball  by  the  pressure  of  the  air,  but  be- 
cause each  aerial  particle  assumes  by  induction  a polarity 
of  the  opposite  kind  on  the  side  nearest  to  the  ball,  and  of 
the  same  kind  on  the  side  farthest  off.  This  state  of  force 
is  therefore  communicated  to  the  interior  of  the  hollow 
sphere,  which  is  electrified  to  the  same  amount,  but  of  an 
opposite  kind  to  the  ball. 

Describe  Bohnenberger’s  electrometer.  What  is  the  basis  of  Faraday’s 
theory  of  induction?  On  this  theory,  are  charges  confined  by  pressure  of  the 
air?  Describe  ihe  action  of  an  electrified  ball  in  the  interior  of  a srdicrc. 

F 


Fig.  102. 


122 


INDUCTIVE  CAPACITIES. 


That  this  polarization  of  the  particles  takes  place,  is  shown 
by  the  position  which  small  silk  fibres  or  spangles  of  gold 
assume  when  placed  in  oil  of  turpentine  through  which  in- 
duction is  established.  Each  particle  disturbs  not  merely 
that  which  is  before  it  or  behind  it,  but  it  is  in  an  active  re- 
lation with  all  surrounding  it,  and  hence  the  polarity  can  be 
propagated  in  curved  lines,  and  induction  take  place  round 
corners  and  behind  obstacles. 


On  these  principles,  we  can  easily  account  for  the  distri- 
bution of  electricity  on  spherical  or  ellipsoidal  conductors, 
the  repulsion  of  bodies  similarly  electrified,  the  condensing 
action  of  the  Leyden  vial,  and  many  other  similar  phe- 
nomena. 

By  a variety  of  experiments.  Dr.  Faraday  has  proved  that 
inductile  action  takes  place  in  curved  lines,  the  directions  of 
which  can  be  varied  by  the  approach  of  bodies.  He  has 
also  shown  that  the  particles  of  solids,  as  gum  lac,  glass,  &c., 
assume  this  character  of  polarity.  Non-conducting  bodies, 
through  which  the  action  of  induction  takes  place,  are  die- 
lectrics, and  each  of  them  has  a specific  induct- 
ive capacity.  Thus,  if  three  metallic  plates, 
ah  c,  Fig.  103,  be  insulated  parallel  to  each 
other,  atmospheric  air  intervening  between 
a and  h,  and  a plate  of  gum  lac  between  b 
and  c,  the  inductive  action  of  the  gum  lac 
will  be  found  to  exceed  that  of  the  air.  The 
^ following  table  gives  some  of  these  results  : ^ 


Inductive  capacity  of  air I’OO 

“ “ glass  . . . : T76 

“ “ lac 200 

“ sulphur 2-24 


All  the  gases  have  the  same  inductive  capacity,  whatever 
their  density,  elasticity,  temperature,  or  hygro metric  con- 
dition may  be. 

The  electrophorus  is  an  instrument  which  depends  for  its 
action  on  induction,  and  is  of  frequent  use  in  chemistry.  It 
consists  of  a cake  of  gum  lac  or  sealing  wax,  b,  Fig.  104, 
on  which  is  placed  a flat  metallic  plate,  a,  with  an  insulating 


Does  induction  take  place  in  straight  or  curved  lines  ? Can  the  particles 
of  solid  bodies  be  polarized  ? What  are  dielectrics  ? What  is  meant  by 
the  specific  inductive  capacity  of  dielectrics  ? Of  air,  glass,  and  sulphur, 
what  are  the  inductive  capacities  ? What  is  the  case  with  gaseous  bodies  ? 
Despribe  the  electrophonis. 


THE  ELECTROPHORUS.  12S^ 

handle,  c.  On  exciting  h with  a piece  of  warm  flannel,  i' 
becomes  negatively  electric,  and  a being 
placed  on  it,  and  the  finger  brought  near,  a 
negative  spark,  driven  from  a by  the  re- 
pulsive influence  of  5,  is  received.  On  lift- 
ing a by  its  insulating  handle,  a positive 
spark  is  obtained  ; on  putting  it  down  on 
h,  a negative  one.  And  in  this  manner 
we  may  obtain  an  unlimited  number  of 
sparks  ; positive  ones  when  a is  lifted,  and  negative  ones 
when  it  is  down.  A little  reflection  will  show  that  none  of 
this  electricity  comes  from  the  excited  cake  h,  but  is  merely 
the  effect  of  its  inductive  influence  on  the  electric  condition 
of  the  metallic  plate  a.  The  electrophorus  may  be  used 
when  the  weather  is  too  damp  for  the  common  machine  to  - 
work. 


LECTURE  XXIX. 

Voltaic  Electricity. — Of  Electricity  in  Motion. — Sul’ 
zer's  Experiment. — Galvani's  Discovery. — Volta's  The’ 
ory.  — Water  is  a compound  Body.  — Description  of  a 
simple  Voltaic  Circle  and  its  Properties. — Direction  of 
the  Current. — Different  Kinds  of  Combinations. — Use 
of  Sulphuric  Acid. — Origin  of  the  Electricity. 

During  the  last  century,  a German  author  of  the  name 
of  Sulzer  observed  that,  when  two  pieces  of  metal  of  difier- 
ent  kinds,  as  silver  and  zinc,  are  placed  one  above  and  the 
other  beneath  the  tongue,  as  often  as  their  projecting  ends 
are  brought  in  contact,  a remarkable  metallic  taste  is  per- 
ceived. To  explain  this  result,  he  supposed  that  some  kind 
of  vibratory  movement  was  excited  in  the  nerves  of  the 
tongue.  It  is  the  first  recorded  phenomenon  attributable  to 
Voltaic  electricity. 

In  the  year  1790,  Galvani,  an  Italian  anatomist,  observed 
the  contractions  which  ensue  when  a metallic  communica- 
tion is  made  between  the  nerves  and  muscles  of  a dead  frog  ; 
he  found  that,  if  a single  metal  is  employed  as  the  line  of 


What  fact  was  first  described  in  Voltaic  electricity  ? What  was  the  fact 
discovered  by  Galvani  ? 


124 


GALVANIC  EXPERIMENTS. 


communication,  contractions  of  the  muscle  take  place  when- 
Fig,  105.  ever  the  metal  reaches  from 

the  nerve  to  the  muscle  ; hut 
that  if  two  pieces  of  different 
kinds  are  used,  the  contrac- 
tions are  much  more  energetic. 
Thus,  if  we  take  the  skinned 
hind  legs  of  a frog,  Fig.  105, 
hanging  together  by  a piece  of 
the  spine,  around  which  tin- 
foil  has  been  twisted,  every 
time  that  we  simultaneously  touch  the  tin-foil  and  the  mus- 
cle with  a bent  copper  wire,  or  with  a copper  and  zinc  wire, 
C Z,  conjointly,  a convulsive  contraction  takes  place. 

To  explain  this  effect,  Galvani  supposed  that  the  muscu- 
lar system  of  animals  is  constantly  in  a positively  electrical 
state,  while  the  nervous  system  is  negative.  In  the  same 
manner,  therefore,  that  a discharge  takes  place  in  the  case 
of  a Leyden  vial,  when  a line  of  communication  is  opened 
between  the  two  coatings,  the  muscular  contractions  in  this 
case  are  to  be  accounted  for.  For  some  time  these  phe- 
nomena went  under  the  name  of  animal  electricity  ; they 
subsequently  have  received  the  designations  of  Galvanism 
and  Voltaic  electricity. 

But  Volta,  another  Italian  philosopher,  was  led  to  suppose 
that  the  cause  of  this  remarkable  result  is  not  due  to  any 
peculiarity  of  the  animal  system,  but  to  the  contact  of  the 
pieces  of  metal  employed.  This  led  to  the  invention  of  the 
Voltaic  pile,  an  instrument  which  has  achieved  a complete 
revolution  in  chemistry. 

It  is  interesting  to  remark  what  great  results  may,  in  the 
hands  of  a true  philosopher,  spring  from  the  most  insignifi- 
cant observations.  The  convulsive  spasms  of  a frog’s  leg 
have  ended  in  showing  that  the  entire  crust  of  the  earth  is 
made  up  of  metallic  oxides,  have  revealed  the  mystery  why 
the  magnetic  needle  points  to  the  north,  and  revolutionized 
the  science  of  chemistry. 

What  we  have  already  said  in  the  foregoing  Lectures  re- 
specting electricity  refers  chiefly  to  that  agent  in  a motion- 
less or  stagnant  state,  as  the  mode  of  its  distribution  on  con- 


In  what  manner  did  he  explain  it?  Under  what  names  did  these  phe- 
nomena successively  pass  ? What  was  Volta’s  supposition  ? What  is  the 
difference  between  common  and  Voltaic  electricity  ? 


THE  SIMPLE  CIRCLE. 


125 


ductors,  the  action  of  the  Leyden  vial,  &c.  The  phenome- 
na of  Voltaic  electricity  are  those  which  arise  from  electric- 
ity in  a state  of  motion. 

From  the  great  advances  which  these  sciences  have  re- 
cently made,  we  are  able  to  present  the  various  topics  in- 
volved in  a much  clearer  way  than  by  merely  tracing  them 
in  a historical  sketch.  I shall  not,  therefore,  pursue  the 
order  in  which  these  facts  were  successively  discovered,  but 
present  them  in  what  now  appears  the  simplest  manner. 

It  is  to  be  admitted,  though  of  that  abundant  proof  will 
soon  be  given,  that  water  is  not  a simple,  but  a compound 
body  ; that  it  consists  of  two  elements,  oxygen  and  hydrogen 
gases.  It  is  also  to  be  understood  that  metallic  zinc  may 
be  amalgamated  or  united  with  quicksilver,  by  putting  it  in 
contact  with  that  fluid  metal,  under  the  surface  of  dilute 
sulphuric  acid.  Strips  of  zinc  thus  amalgamated  exhibit  a 
pure  metallic  brilliancy. 

If  now  we  take  a strip  of  amalgamated  zinc,  an  inch 
wide  and  three  or  four  inches  long,  and  a piece  of 
clean  copper  of  similar  size,  2:  and  c.  Fig.  106,  and 
placing  them  side  by  side  in  a glass, containing 
water  slightly  acidulated  with  sulphuric  acid,  we 
have  one  of  the  forms  of  a simple  Voltaic  circle. 

In  this,  it  is  to  be  observed,  that  so  long  as  the  me- 
tallic plates  remain  without  touching  each  other, 
no  remarkable  phenomenon  appears  ; but  if  we 
take  a metallic  rod,  d,  and  let  it  connect  the  top  of  the  zinc 
and  copper  together,  a series  of  new  facts  arises. 

First,  from  the  surface  of  the  copper,  bubbles  of  gas  are 
evolved ; they  are  minute,  but  so  numerous  as  to  make  the 
water  turbid ; if  collected,  they  are  found  to  be  hydrogen  gas. 

Secondly,  the  plate  of  zinc  rapidly  wastes  away,  as  is  easi- 
ly proved  by  weighing  it  from  time  to  time  ; and  on  exam- 
ining the  liquid  in  the  cup,  we  discover  the  cause  of  this 
waste,  for  that  liquid  contains  oxide  of  zinc  ; coupling  this 
fact  with  the  former,  we  infer  that,  so  long  as  the  metallic 
rod,  d,  is  in  its  place,  water  is  decomposed,  its  oxygen  unit- 
ing with  the  zinc,  its  hydrogen  escaping  from  the  copper. 
On  removing  the  rod,  d,  all  these  phenomena  at  once  cease. 

Is  water  a simple  or  a compound  body  ? What  is  meant  by  amalgamated 
zinc?  Describe  a simple  Voltaic  circle.  As  long  as  the  plates  are  not  in 
contact,  does  any  phenomenon  take  place  ? On  communicating  by  a metal- 
lic rod,  what  gas  is  evolved  from  the  copper?  What  happens  to  the  zinc? 
Why  do  wc  infer  that  water  is  decomnosed  ? 


126 


PHENOMENA  OF  A SIMPLE  CIRCLE. 


Thirdiji,  if,  instead  of  a metallic  rod,  c?,  a rod  of  glass,  or 
other  non.'-v^onductor  of  electricity,  be  employed,  no  decom- 
position tifcii.es  place.  This,  therefore,  indicates  that  the 
agent  which  is  in  operation  is  electricity. 

Fourthly,  if  for  the  line  of  communication,  d,  a piece  of 
metal  he  employed,  and  we  cautiously  lift  it  from  the  zinc 
or  copper  plate,  the  moment  the  contact  is  broken,  in  a dark 
room,  we  see  a minute  electric  spark.  It  has  been  already 
observed  that  the  electric  spark  can  not  he  confounded  with 
any  other  natural  phenomenon. 

Fifthly,  if  the  line  of  communication  he  a very  slender 
platinum  wire,  as  long  as  it  remains  in  its  position,  its  tem- 
perature rises  so  high  tnat  it  becomes  red  hot,  and  may  he 
kept  so  for  hours  together.  Now,  recollecting  that  the  igni- 
tion and  fusion  of  metals  take  place  when  they  are  made  to 
intervene  between  the  coatings  of  a Leyden  vial,  and  con- 
sidering all  the  facts  which  have  just  been  set  forth,  we  see 
that  the  following  conclusion  may  be  drawn : that  in  an 
active  simple  Voltaic  circle  water  is  decomposed,  its  oxygen 
going  to  the  zinc  and  its  hydrogen  to  the  copper,  and  that 
a continuous  current  of  electricity  accompanies  this  decom- 
position, running  from  one  metal  to  the  other,  through  the 
connecting  rod. 

The  direction  of  this  current  may  he  determined  by  sev- 
eral processes  ; it  is  as  follows  : the  electricity,  leaving  the 
surface  of  the  zinc,  passes  thrtugh  the  liquid  to  the  copper, 
then  moves  through  the  connecting  wire  back  again  to  the 
zinc,  performing  a complete  circuit ; hence  the  term  Voltaic 
circle. 

Simple  Voltaic  circles  are  of  several  kinds ; that  which 
we  have  been  considering  consists  of  two  different  metals 
with  one  intervening  liquid,  but  similar  results  can  be  ob- 
tained with  one  piece  of  metal  and  two  different  liquids. 

In  the  foregoing  experiment  we  have  used  dilute  sul- 
phuric acid  : this  acid  discharges  a subsidiary  duty.  Zinc, 
when  it  oxidizes,  is  covered  with  a coating  impermeable  to 
water  and  air ; it  is  this  grayish  oxide  which  protects  the 
common  sheet  zinc  of  commerce  from  farther  change. 
"When,  therefore,  a Voltaic  pair  gives  rise  to  a current  by 

If  a glass  rod  is  used  instead  of  a metallic  one,  what  is  the  result  ? How 
can  a spark  be  made  visible  ? Can  a platinum  wire  be  ignited  ? From  these 
facts,  what  conclusions  may  be  drawn  ? What  is  the  course  of  the  current  ? 
What  other  kinds  of  Voltaic  circles  are  there  ? 


ELECTROMOTIVE  SOURCE. 


127 


the  oxydation  of  its  zinc,  that  current  would  speedily  stop 
were  not  the  oxide  removed  as  fast  as  it  forms  ; this  is  done 
by  the  sulphuric  acid,  which  forms  with  it  a sulphate  of 
zinc,  a substance  very  soluble  in  water,  and  the  metal  thus 
continually  presents  a clear  surface  to  the  water. 

As  to  the  immediate  cause  which  gives  rise  to  the  Voltaic 
current,  there  has  been  a difference  of  opinion  among  chem- 
ical authors.  Volta  believed  that  the  mere  contact  of  the 
metals  was  the  electromotive  source,  and  endeavored  to 
prove,  by  direct  experiment,  that  if  a piece  of  copper  and 
zinc  are  brought  in  contact  and  then  separated,  they  become 
excited,  the  one  positively  and  the  other  negatively  ; upon 
these  principles,  he  was  led  to  the  discovery  of  the  Voltaic 
battery.  But  many  facts  have  now  indisputably  shown  that 
the  origin  of  the  current  is  to  be  sought  in  the  chemical 
changes  going  on  ; and  in  the  instance  we  have  had  under 
consideration,  it  is  due  to  the  decomposition  of  water.  That 
the  electromotive  action  does  not  depend  on  the  contact  of 
the  metals,  seems  to  be  proved  by  the  fact  that,  by  chang- 
ing the  nature  of  the  liquid  intervening  between  them,  we 
can  change  the  current  both  in  direction  and  force. 


LECTURE  XXX. 

Effects  of  Voltaic  Electricity. — Invention  of  the  Vol- 
taic Pile. — CruickshanP s Trough. — Hare's  Battery. 
— Smee's  Simple  and  Compoujid  Battery.  — Grove's 
Battery. — Voltaic  Effects,  the  Spark,  Deflagration  of 
Metals. — Ignition  of  Wires. — Arc  of  Flame. — Decom- 
position of  Water. — Nature  of  the  Gases  evolved. 

It  has  been  already  observed  that,  in  the  discussions 
which  arose  respecting  animal  electricity,  Volta  attributed 
the  action  entirely  to  the  metals  employed,  and,  reasoning 
on  this  principle,  he  concluded  that  the  effect  ought  to  in- 
crease, if,  instead  of  using  a single  pair  of  metals,  a great 
number  of  alternations  were  employed.  Accordingly,  on 

What  is  the  use  of  sulphuric  acid  in  these  combinations  ? What  was 
Volta’s  opinion  as  to  the  electromotive  source  ? What  is  the  view  now 
taken  ? What  arguments  may  be  adduced  for  its  correctness  ? How  was 
Volta  led  to  the  invention  of  the  pile  ? 


128 


THE  VOLTAIC  TILE. 


taking  thirty  or  forty  silver  coins  and  discs  of  zinc,  and  pieces 
of  cloth  moistened  with  acidulated  water,  of  the  same  size, 
and  arranging  them  in  a pile  or  column,  carefully  observing 
Fig.  107.  to  place  them  in  the  same  order,  silver,  cloth, 
zinc — silver,  cloth,  zinc,  &c.,  he  found  his  ex- 
pectation verified.  On  touching,  with  moist- 
ened hands,  the  end  of  the  pile,  a shock  was  at 
once  received,  and  on  making  them  communi- 
cate by  a piece  of  wire,  an  electric  spark  passed. 
This  instrument.  Fig.  107,  is  the  Voltaic  pile. 
From  the  important  uses  to  which  the  pile  was  soon  de- 
voted, it  became  necessary  to  have  it  under  a more  conve- 
nient form.  There  are  several  inconveniences  attending 
the  original  construction  : it  is  liable  to  overset,  is  trouble- 
some to  put  in  action,  and  requires  to  be  taken  to  pieces 
and  carefully  cleaned  every  time  it  is  used ; its  maximum 
effect  lasts  but  a short  time,  owing  to  the  weight  of  the  su- 
perincumbent column  pressing  out  the  moisture  from  the 
lower  pieces  of  cloth ; and  as  soon  as  they  become  dry,  all 


action  ceases. 

These  difficulties  were  avoided,  to  a great  extent,  in  the 
trough  battery,  which  soon  replaced  the  former  instrument. 

Fig.  108.  It  consists  of  a box 

or  trough.  Fig.  108, 
three  or  four  inches 
square  at  the  ends,  and 
a foot  or  more  long ; 
grooves  are  made  in 
the  sides  and  bottom 
of  this  box,  and  into  them  pieces  of  zinc  and  copper,  soldered 
face  to  face,  are  fastened,  water  tight,  by  cement.  These 
grooves  are  about  half  an  inch  apart,  and  into  their  inter- 
stices acidulated  water  is  poured,  care  being  taken  that  the 
metals  are  arranged  in  the  same  direction,  so  that  if  the  se- 
ries begins  with  a copper  plate,  it  ends  with  a zinc.  The 
apparatus  is  obviously  equivalent  to  Volta’s  pile  laid  on  its 
side,  and  the  facility  for  charging  it,  and  removing  the  acid 
when  the  experiments  are  over,  is  very  great.  From  the 
extremities  two  flexible  copper  wires  pass  : they  are  called 
the  polar  wires,  or  electrodes  of  the  battery. 


Describe  the  Voltaic  pile.  What  are  its  effects  ? What  inconveniences 
are  there  in  the  original  form  ? Describe  the  trough  battery.  Describe 
some  of  the  improvements  in  the  battery. 


hare’s,  danieli/s,  and  simee’s  batteries.  129 


Fig.  109. 


Some  very  convenient  forms  of  Voltaic  battery  have  been 
invented  by  Dr.  Hare.  In  one  of  these,  the  liquid  is  poured 
off  and  on  the  plates  by  a quarter  revolution  of  a handle  ; 
in  others,  the  trough  is  made  movable,  so  that  it  lifts  up 
when  all  the  arrangements  are  ready,  and  the  plates  are 
immersed. 

In  almost  all  the  recently  improved  forms  of  Voltaic  bat- 
tery, the  zinc  is  amalgamated.  This  prevents  what  is  term- 
ed local  action — a waste  in  which  much  metal  is  consumed 
without  adding  to  the  power  of  the  current,  and  Avhich  like- 
wise deteriorates  the  acid  liquid  by  the  accumulation  of  sul- 
phate of  zinc.  When  amalgamated,  all  the  zinc  consumed 
aids  in  the  current. 

When  it  is  required  to  have  a current,  the 
intensity  of  which  remains  constant  for  a length 
of  time,  Daniell’s  battery  is  to  be  preferred.  It 
consists  of  a copper  cylinder,  C,  Fig.  109,  in 
which  a solution  of  sulphate  of  copper  is  poured ; 
within  this  is  a second  cylinder,  P,  of  porous 
earthen- ware,  filled  with  dilute  sulphuric  acid, 

A,  into  which  an  amalgamated  zinc  rod,  Z, 
dips.  From  the  copper  and  zinc,  rods  project, 
terminated  by  binding  screws,  with  which  the 
polar  wires  may  be  connected. 

Smee’s  battery  is  also  a very  valuable  com- 
bination  : it  consists  of  a plate  of  platinized  sil- 
ver,  or  platinized  platinum,  S,  Fig.  110,  on  each  side  of 
which  are  placed  parallel  plates  of  amalgamated  zinc,  Z ; 
these  plates  are  held  tightly  against  a piece  Fig.  no. 
of  wood,  10,  by  means  of  a clamp,  b,  to 
which,  and  also  to  the  silver  plate,  bind- 
ing screws,  for  the  purpose  of  fastening 
polar  wires,  are  affixed.  The  whole  is  = 
suspended,  by  means  of  a cross-piece  of 
wood,  in  ajar  containing  dilute  sulphuric 
acid. 

Smee’s  compound  battery,  represented  !i||i 
in  Fig.  Ill,  is  nothing  more  than  a series  || 
of  the  foregoing  simple  circles.  The  figure 
shows  one  containing  six  cells;  the  posi- 
tion  of  the  platinized  silver  and  zinc  plates 

Wliaf  arc  the  forms  introduced  by  Hare,  Daniell,  Since,  and  Gk 
sjiectively  ? 

F 2 


130 


grove’s  battery. 


of  one  of  the  pairs  is  seen  at  S and  Z.  It  is  to  be  charged 
with  dilute  sulphuric  acid. 

Fig.  111. 


Probably  the  most  powerful  of  all  Voltaic  combinations 
is  the  instrument  invented  by  Mr.  Grove.  It  consists  of  two 
Fig.  112.  metals  and  two  liquids,  amalgamated  zinc  and 
platina,  dilute  sulphuric  acid  and  strong  nitric  acid. 
Ajar,  P,  Fig.  112,  three  quarters  of  an  inch  in 
diameter,  and  made  of  porous  or  unglazed  earthen- 
ware, is  to  be  filled  with  strong  nitric  acid,  N,  and 
in  it  a slip  of  platina  is  placed ; this  porous  earthen- 
ware cup  is  then  set  in  a glass  cup,  A,  nearly  three 
inches  in  diameter;  in  this  is  placed  a plate  of 
zinc,  Z,  one  eighth  of  an  inch  thick,  and  of  such 
a size,  as  respects  its  other  dimensions,  that  it  will 
readily  pass  between  the  porous  cup,  P,  and  the 
glass.  In  the  glass,  A is  placed  dilute  sulphjuric 
acid. 

In  this  manner  several  cups  are  to  be  provided,  the  ar- 
rangement being,  zinc  in  contact  with  dilute  sulphuric  acid, 
and  platina  in  contact  with  strong  nitric  acid,  with  a porous 
cup  intervening  between.  The  workman  also  previously 
connects  each  zinc  cylinder  with  the  slip  of  platina,  which 
is  in  the  next  cup,  by  soldering  between  them  a strip  of 
copper. 

Grove’s  battery  owes  its  force  to  the  decomposition  of 
water  by  zinc.  But  the  hydrogen  is  not  evolved  from  the 
surface  of  the  platina,  as  it  would  be  in  a single  circle  ; it 
is  here  taken  up  by  the  nitric  acid,  which  undergoes  rapid 
deoxidation,  and  therefore,  during  the  use  of  this  battery, 
volumes  of  deutoxide  of  nitrogen  are  evolved.  A battery  of 
fifty  cups  gives  rise  to  very  striking  effects ; but  five  or  ten 
are  quite  sufficient  to  repeat  all  the  following  experiments. 


What  are  the  chemical  effects  taking  place  in  Grove’s  battery  ? 


DEFLAGRATION  OF  METALS. 


131 


Fig.  113. 


On  separating  the  polar  wires  of  such  a battery  from  each 
other,  a brilliant  spark  passes,  and,  if  the  separation  be  grad- 
ual, a flame  constantly  proceeds  from  one  to  the  other  ; the 
light  of  which,  when  the  wires  are  of  copper,  is  of  a beauti- 
ful green  color. 

If,  on  the  surface  of  some  quicksilver  contained  in  a glass. 
Fig.  113,  we  lower  a thin  piece  of  steel, 
or  iron  wire,  connected  with  one  of  the 
poles  of  the  battery,  the  mercury  being 
kept  in  contact  with  the  other,  the  steel  . 
takes  fire  and  deflagrates  beautifully,  emit- 
ting bright  sparks,  and  the  mercury  is  rap- 
idly volatilized. 

When  thin  metal  leaves  are  made  to  in- 
tervene between  the  polar  wires,  they  are 
at  once  dissipated,  the  flames  they  emit  being  of  diflerent 
colors  in  the  case  of  different  metals. 

If  a piece  of  platinum  wire  is  made  the  channel  of  com- 
munication from  one  pole  to  the  other,  if  it  does  not  fuse  at 
once,  it  becomes  incandescent,  and  remains  so  as  long  as  the 
instrument  is  in  activity. 

When  the  polar  wires  are  terminated  by  pieces  of  well- 
burned  charcoal,  or  that  variety  of  carbon  which  is  formed 
in  the  interior  of  gas  retorts,  the  light  which  passes  between 
them  when  they  are  removed  from  contact  is  one  of  the 
most  brilliant  that  can  be  obtained  by  any  artificial  means. 
With  powerful  batteries,  the  pieces  of  charcoal  may  be  sep- 
arated several  inches  apart  without  the  light  ceasing,  and 
then  it  moves  from  one  pole  to  the  other  in 
an  arched  form.  Fig.  114,  the  convexity 
of  the  arc  being  upward.  This  form  is 
due  to  the  current  of  hot  air  which  rises  from  the  ignited  space 
between  the  poles,  and  the  light  may  be  blown  out  by  the 
mouth,  just  in  the  same  manner  that  we  blow  out  a candle. 

But,  in  a scientific  point  of  view,  by  far  the  most  interest- 
ing experiment  to  be  made  with  the  Yoltaic  battery  is  the 
decomposition  of  water.  Through  the  bottom  of  a glass 
vase  or  dish,  at  the  point  a b,  Fig.  115,  two  platinum  wires 


On  separating  the  polar  wires  of  a battery,  what  phenomenon  arises  ? 
How  may  iron  wire  be  deflagrated?  Wliat  phenomenon  is  seen  during  the 
deflagration  of  metallic  leaves  ? When  a thin  platinum  wire  communicates 
between  the  poles,  what  is  the  result  ? How  is  the  arc  of  light  formed,  and 
what  are  its  properties  ? Describe  the  process  for  the  decomposition  o( 
water. 


132 


DECOMPOSITION  OF  WATER. 


Fiff.  115.  are  introduced,  water-tight ; they  pass 
into  the  vase,  as  a c,  b parallel  to  each 
other,  hut  not  touching.  Over  each  of 
these  wires  a tube  is  to  be  inverted  ; the 
tube  e over  c,  andjT  over  the  vase  and 
the  tubes  being  previously  filled  with 
water  acidulated  slightly,  to  improve  its 
conducting  power.  Now  let  the  wire 
a c be  connected  with  the  positive  pole 
of  the  Voltaic  battery,  and  h d with  the  negative  ; bubbles 
of  gas  in  a torrent  arise  from  their  extremities,  and  pass  up- 
ward in  the  tubes,  displacing  the  water.  The  quantity  of 
gas  thus  collecting  in  the  two  tubes  is  unequal,  and  when- 
ever we  stop  the  decomposition  there  will  be  found  in  f 
double  the  quantity  which  is  in  e.  When  a sufficient  amount 
is  collected,  let  the  tube  e,  containing  the  smaller  portion  of 
gas,  be  cautiously  removed,  preventing  any  atmospheric  air 
from  getting  into  its  interior,  by  closing  it  with  the  finger, 
and  then,  turning  the  tube  upside  down,  let  a stick  of  wood, 
with  a spark  of  fire  on  its  extremity,  be  immersed  in  the  gas. 
In  a moment  the  wood  bursts  into  a flame,  proving  that  this 
is  oxygen  gas.  Then  take  the  other  tube,  and  allow  to  pass 
into  it  a quantity  of  atmospheric  air  equal  to  the  volume  of 
gas  it  already  holds  ; remove  the  finger  and  apply  a light, 
and  there  is  an  explosion.  But  this  is  the  property  of  hy- 
drogen gas.  We  therefore  conclude  that  in  this  experiment 
water  has  been  decomposed  and  resolved  into  its  constituent 
ingredients,  oxygen  and  hydrogen  ; and,  farther,  that  in 
Fig.  116.  water  there  is,  by  volume,  twice  as  much 

H hydrogen  as  there  is  oxygen  gas.  The  sep- 
aration of  the  two  is  perfect,  so  much  so 
that  the  decomposition  may  be  conducted 
in  different  vessels.  Thus,  let  N and  P be 
tubes,  through  the  closed  upper  ends  of 
v^hich  platinum  wires  pass  ; invert  them 
in  glasses  of  water,  with  a siphon  of  large 
^ bore  connecting  them.  On  making  N com- 
municate with  the  negative,  and  P with 
the  positive  pole,  decomposition  ensues,  hydrogen  gas  accu- 
mulating in  N,  and  oxygen  in  P. 

What  is  the  relative  proportion  of  the  gases  collected  ? How  can  it  be 
■p-oved  that  the  less  quantity  is  oxygen  and  the  larger  hydrogen  ? What  is 
ne  constitution  of  water  by  volume  ? 


POL  All  DECOMPOSITION. 


133 


LECTUUE  XXXI. 

The  Electro-chemical  Theory. — Theory  of  the  Decom- 
2Wsition  of  Water.  — Decomiiosition  of  Metallic  and 
other  Salts. — BecquereV s Illustration  of  the  Formation 
of  Minerals.  — Davy's  Discoveries.  — Electro-chemical 
Theory. — Electrolytes. — Faraday's  Theory  of  definiie 
Action. — The  Electrotype. 

The  prominent  fact  connected  with  the  decomposition  of 
water  is  the  total  separation  of  the  constituent  elements  on 
the  opposite  polar  wires  or  electrodes.  From  the  positive 
wire  oxygen  alone  escapes,  and  from  the  negative  hydrogen  ; 
there  is  no  partial  admixture,  but  the  separation  is  perfect 
and  complete. 

Though  the  polar  wires  may  be  separated  from  each  other 
by  a considerable  distance,  the  same  result  is  uniformly  ob- 
tained, and  it  is  to  be  remarked  that  the  evolution  of  gas 
takes  place  on  the  wires  alone  ; no  intervening  bubbles 
make  their  appearance  in  the  intermediate  space.  The 
principle  on  which  this  is  effected  may  be  easily  understood, 
by  supposing  H H and  O 0,  Fig.  117,  to 
represent  atoms  of  hydrogen  and  oxygen  o ' 
respectively  ; each  pair  of  them,  therefore,  ' 
represents  a particle  of  water.  Now,  if 
we  slide  the  upper  row  of  atoms  upon  the  r 
lower,  as  shown  at  h A,  o o,  it  is  obvious 
that  a hydrogen  atom  will  be  set  free  at  one  extremity  of 
the  line,  and  an  oxygen  atom  at  the  other,  and  that,  as  re- 
spects all  the  intermediate  pairs  of  atoms,  though  they  have 
changed  their  places,  yet  every  particle  of  hydrogen  is  still 
associated  with  a particle  of  oxygen,  constituting,  therefore, 
a particle  of  water ; and  it  is  at  the  extremes  of  the.  line 
alone  that  the  gases  are  set  free.  So  in  the  polar  decom- 
position by  the  pile,  all  the  liquid  intervening  between  the 
poles  is  affected,  decompositions  and  recombinations  suc- 
cessively taking  place,  the  hydrogen  atoms  moving  in  one 


Do  these  polar  decompositions  effect  a total  separation  of  the  bodies  ? In 
the  decomposition  of  water,  do  any  gas  bubbles  appear  in  the  intervening 
space  ? liow  is  tliis  explained  ? How  is  it,  if  dtcoinpositions  are  going  on 
in  the  intervening  space,  that  the  gases  are  not  there  seen  ? 


O 

H 


I' 

i 

K 

134 


VOLTAIC  DECOMPOSITIONS. 


direction,  the  oxygen  in  the  other,  finally  to  be  set  free  on 
the  surface  of  the  polar  wires. 

This  capital  discovery  of  the  decomposition  of  water  by 
Voltaic  electricity  was  originally  made  by  Nicholson  and 
Carlyle.  It  is  by  far  the  most  satisfactory  method  of  dem- 
onstrating the  constitution  of  that  liquid.  After  it  was  made 
known,  any  lingering  doubts  which  still  remained  on  the 
minds  of  some  chemists  in  relation  to  the  composite  nature 
of  water  were  speedily  removed. 

In  the  same  manner  that  water  is  decomposed  by  the 
Voltaic  battery,  so,  also,  many  metallic  and  other  salts  yield 
to  its  influence.  Thus,  if  into  ajar  containing  a solution 
of  blue  vitriol,  the  sulphate  of  copper,  two  metallic  plates 
are  introduced  parallel  to  each  other,  and  one  of  them 
brought  in  connection  with  the  negative  and  the  other  with 
the  positive  pole  of  the  battery,  decomposition  of  the  salt 
takes  place ; the  sulphate  of  copper  being  resolved  into  its 
constituents,  sulphuric  acid  and  the  oxide  of  copper,  and  the 
latter  reduced  to  the  condition  of  metallic  copper  by  hydro- 
gen simultaneously  evolved  with  it;  arising  from  the  decom- 
position of  a part  of  the  water.  In  this  manner  the  copper 
may  be  deposited,  with  a little  care,  under  Ijie  form  of  a 
tough  metallic  mass. 

If  in  a cubical  glass  vessel,  Fig.  118,  divided  into  two 


decomposition  of  the  iodide  takes  place,  its  iodine  being 
evolved  at  the  positive  wire,  and  giving  with  the  starch  a 
deep  blue  color,  the  blue  iodide  of  starch,  while  the  liquid 
in  the  other  partition  remains  colorless. 

M.  Becquerel  obtained  some  very  beautiful  results  by  the 
aid  of  weak  but  long-continued  electric  currents,  illustrating 
the  probable  mode  of  formation  of  mineral  substances  by 
such  currents  traversing  the  crust  of  the  earth.  If  we  take 
a glass  tube  bent  into  the  form  of  a U,  and  close  the  bended 

Can  metallic  salts  be  in  like  manner  decomposed  ? Describe  the  polar 
decomposition  of  iodide  of  potassium.  Can  decompositions  be  produced  by 
very  feeble  Voltaic  currents  ? 


Fig.  118. 


partitions  by  a diaphragm, 


^ a,  and  both  partitions  filled 
with  a solution  of  iodide  of 
potassium,  mixed  with  a 
M solution  of  starch,  and  the 
positive  and  negative  wires 
of  the  battery  introduced, 


BECaUERELS  EXPERIMENTS. 


135 


Fig.  119. 


Fig.  120. 


part  with  a plug  of  plaster  of  Paris,  putting 
in  one  of  the  branches  a solution  of  car- 
bonate of  soda,  and  in  the  other  of  sulphate 
of  copper,  immersing  in  one  of  the  solutions 
a zinc  plate,  and  in  the  other  a copper, 
connected  together  by  a piece  of  bent  wire, 
the  liquids  communicate  through  the  porous 
plug,  and  crystals  of  the  double  carbonate 
of  copper  and  soda  form  on  the  plate  im- 
mersed in  the  copper  liquid.  In  the  same 
manner,  other  compound  salts  and  mineral  bodies  may  be 
produced. 

Or  if  we  take  a jar,  A,  and  fill  it  with  a so- 
lution of  nitrate  of  copper  to  a,  and  then  with 
dilute  nitric  acid  to  B,  and  immerse  in  it  a slip 
of  copper,  C D,  presenting  equal  surfaces  to  the 
two  liquids,  an  electric  current  is  generated,  the  - 
copper  is  dissolved  in  the  upper  solution,  and  is 
deposited  in  crystals  at  D in  the  lower. 

As  in  this  manuer  water  and  various  saline 
bodies  undergo  decomposition  by  the  action  of 
the  pile,  it  occurred  to  Sir  H.  Davy  that  proba- 
bly other  substances,  at  that  time  supposed  to  be 
simple,  might  also  be  decomposed.  He  accordingly  subject- 
ed the  alkaline  and  earthy  bodies,  then  reputed  to  be  ele- 
mentary, to  the  influence  of  a powerful  battery,  and  found 
that  his  supposition  was  verified.  On  placing  a fragment 
of  caustic  potash  between  the  poles,  it  immediately  melted ; 
from  the  positive,  oxygen  gas  escaped  in  bubbles,  and  from 
the  negative,  small  metallic  globules,  having  the  appear- 
ance of  quicksilver,  emerged  ; these  were  characterized, 
however,  by  the  singular  qualities  of  an  intense  affinity  for 
oxygen,  so  that  they  would  take  fire  on  being  touched  by 
water,  or  even  ice,  and  were  so  light  as  to  swim  upon  the 
surface  of  that  liquid. 

The  result  of  Davy’s  experiments  proved  that  the  alka- 
line substances  and  all  the  earths  are  oxidized  bodies,  and 
in  most  instances  oxides  of  metals. 

On  these  principles,  Davy  established  a division  of  ele- 
mentary bodies  into  electro- positive  and  electro-negative 

Describe  some  of  the  arrangements  of  M.  Becquerel  for  illustrating  the 
probable  mode  of  formation  of  minerals.  What  were  the  discoveries  of 
Davy  respecting  the  alkaline  and  earthy  bodies  ? 


]36 


ELECTRO-CHEMICAL  THEORY. 


substances.  The  former  are  those  which,  during  a polar 
decomposition,  go  to  the  negative  pole,  and  the  latter  those 
that  go  to  the  positive.  The  electro-chemical  theory  as- 
sumes that  all  bodies  have  a natural  appetency  for  the  as- 
sumption of  the  positive  or  negative  states  respectively,  and 
that  all  the  phenomena  of  chemical  combination  are  mere- 
ly cases  of  the  operation  of  the  common  law  of  electrical 
attraction  ; for  between  particles  in  opposite  states  attrac- 
tion ought  to  take  place,  and  when  in  a compound  body, 
such  as  water,  which  consists  of  particles  of  negative  oxy- 
gen and  positive  hydrogen,  the  poles  of  an  active  Voltaic 
battery  are  immersed,  they  will  effect  its  decomposition,  the 
negative  oxygen  going  to  the  positive  pole,  and  the  positive 
hydrogen  to  the  negative  pole. 

Davy’s  theory  thus  not  only  accounts  for  the  decomposing 
agencies  of  the  battery,  but  also  for  all  common  cases  of 
chemical  combination,  referring  both  to  the  fundamental 
law  of  electric  attraction.  With  all  its  simplicity,  it  would 
be  very  easy  to  show,  however,  that  it  is  founded  on  a 
groundless  assumption,  and  can  not  account  for  a great  num- 
ber of  well-known  facts. 

The  Voltaic  pile  can  not  decompose  all  bodies  indiscrim- 
inately. An  electrolyte — for  so  a decomposable  substance 
is  termed — must  always  be  a fluid  body.  It  also  appears 
that  all  electrolytes  must  have  a binary  constitution,  or  con- 
tain one  atom  of  each  of  their  two  constituent  ingredients. 

Mr.  Faraday  discovered  that  the  action  of  an  electric  cur- 
rent in  effecting  the  decomposition  of  various  bodies  is  per- 
fectly definite  : thus,  if  we  make  the  same  current  pass 
through  a series  of  vessels  containing  water,  iodide  of  po- 
tassium, melted  chloride  of  lead,  they  will  all  be  decom- 
posed, but  in  very  different  quantities.  If  of  the  w^ater  there 
be  decomposed  9 parts,' there  will  be  165  of  iodide  of  potas- 
sium, and  139  of  chloride  of  lead  ; but  these  numbers  rep- 
resent what  will  be  hereafter  given  as  the  atomic  weights 
of  the  bodies  in  question.  A current  which  can  set  free  one 
grain  of  hydrogen  will  evolve  108  of  silver,  104  of  lead,  39 
of  potassium,  31-6  of  copper,  &c.,  these  being  the  atomic 
weights  of  those  substances  respectively. 

What  is  meant  by  the  electro-chemical  theory  ? Does  this  theory  also 
account  for  chemical  combination  ? To  what  bodies  is  the  decomposing  in- 
fluence of  the  Voltaic  battery  limited  ? Gan  substances  other  than  binary 
compounds  be  thus  decomposed?  Explain  Faraday’s  law  of  the  definite 
action  of  a Voltaic  cunent. 


THE  ELECTROTYPE. 


137 


A very  beautiful  application  of  electro-chemical  decom- 
position has  of  late  been  introduced  into  the  arts.  It  passes 
under  the  name  of  the  electrotype.  It  consists  in  the  pre- 
cipitation of  metallic  copper,  gold,  silver,  platina,  &c.,  on 
different  surfaces,  by  the  aid  of  a Voltaic  current.  Thus, 
suppose  it  were  required  to  obtain  a perfect  copy  in  copper 
of  one  of  the  faces  of  a medal ; let  Fig.  121. 

a glass  trough,  N O^Fig.  121,  be 
filled  with  a solution  of  the  sul- 
phate of  copper,  and  to  the  nega- 
tive wire,  Z,  of  a Smee’s  Voltaic 
battery,  let  the  medal  N be  at- 
tached, all  those  portions,  except 
the  face  designed  to  be  copied,  be- 
ing varnished  over,  or  covered 
with  wax,  to  protect  them  from 
contact  with  the  liquid.  To  the 
positive  wire,  S,  let  there  be  attached  a mass  of  copper,  C. 
As  soon  as  the  battery  is  in  action,  decomposition  of  the 
sulphate  takes  place,  metallic  copper  is  precipitated  on  the 
face  of  the  medal,  copying  it  with  surprising  accuracy.  This 
copper  is,  of  course,  withdrawn  from  the  sulphate  in  the  so- 
lution ; but  while  this  is  going  on,  sulphuric  acid  and  oxy- 
gen are  being  evolved  on  the  mass  of  copper,  C.  They 
therefore  unite  with  it ; and  thus,  as  fast  as  copper  is  pre- 
cipitated on  N by  oxydation,  new  quantities  are  obtained 
from  C,  and  the  liquid  keeps  up  its  strength  unimpaired. 
In  the  course  of  a day  the  medal  may  be  removed.  It  will 
be  found  incrusted  with  a tough,  red  coat  of  Fig.  122. 
copper,  which  may  be  readily  split  off  from 
it.  It  is  a perfect  copy  of  the  surface  on 
which  the  deposition  took  place,  and,  in  turn, 
it  may  be  used  as  a mould  for  obtaining  a 
great  number  of  casts.  Gilding,  silver-plat- 
ing, and  platinizing  are  now  performed  on 
the  same  principles,  the  electrotype  being 
one  of  the  most  beautiful  contributions  which 
science  has  of  late  given  to  the  arts. 

An  instrument,  the  Voltameter,  has  been 
invented  by  Mr.  Faraday  for  measuring  quan- 
tities of  Voltaic  electricity.  It  is  represent- 
ed in  Fig.  122.  It  consists  of  a glass  j:»r, 


Describe  the  electrotype. 


138  DIFFERENT  VOLTAIC  BATTERIES. 

filled  to  the  height  d with  water,  and  through  its  cover, 
c,  a graduated  tube,  passes.  In  the  lower  part  of  the 
tube  at  g,  two  pieces  of  platina-foil,  which  form  the  term- 
inations of  the  polar  wires  of  the  battery,  the  current  of 
which  is  to  be  measured,  are  introduced,  the  connection  with 
those  wires  being  made  by  the  aid  of  the  mercury  cups,  e f. 
The  tube,  a,  having  been  filled  with  water,  as  soon  as  the 
current  passes  decomposition  takes  place,  the  gases  collect- 
ing in  the  graduated  tube,  and  measuring  the  amount  of 
the  current. 


LECTURE  XXXII. 

Ohm’s  Theory  of  the  Voltaic  Pile.  — Magnetism  and 
Electro-magnetism. — Volta's  Pile. — Hare's  Calorim- 
otor.  — Zamboni's  Pile. — Ohm's  Theory. — Electro-mo- 
live  Force. — Resistance. — General  law  for  the  Force  of 
the  Current. — Laws  and  Phenomena  of  Magnetism. — 
Electro-magnetism,  Oersted' s Discoveries  in. — The  Gal- 
vanometer. — Electric  Rotations.  — Tangential  Force. 
— Electro-magnets. 

With  a given  amount  of  metallic  surface  we  can  produce 
Voltaic  batteries  having  different  qualities.  Thus,  if  we 
take  a square  foot  of  copper  and  a square  foot  of  zinc,  and 
place  between  them  a piece  of  wet  cloth,  we  shall  have  a 
battery  which  can  not  give  shocks,  nor  effect  the  decompo- 
sition of  water,  but  which  will  cause  a fine  metallic  wire  to 
become  white  hot,  or  even  to  fuse.  If,  again,  we  take  a 
square  foot  of  copper  and  a square  foot  of  zinc,  and  cut  each 
into  144  plates,  an  inch  square,  and  arrange  them  with  sim- 
ilar pieces  of  cloth  as  a Voltaic  pile,  the  instrument  will  give 
shocks,  and  decompose  water  rapidly.  From  the  same  quan- 
tity of  metal  two  different  species  of  battery  may  be  made  ; 
one  consisting  of  a few  plates  of  large  surface,  or  one  of  a 
great  number  of  alternations  of  smaller  plates. 

Of  these  varieties  of  battery,  the  calorimotor  of  Dr.  Hare 
is  an  example  of  the  first.  It  consists  of  a series  of  zinc 
plates,  all  connected  together,  and  one  of  copper,  also  simi- 
larly connected,  constituting  therefore,  in  reality,  a single  pair 

Describe  the  Voltameter.  What  are  the  two  principal  forms  of  battery? 
What  does  the  calorimotor  illustrate  ? 


OHM  S THEORY  OF  VOLTAIC  CURRENTS. 


139 


of  very  large  surface.  The  great  amount  of  heat  evolved  by 
this  apparatus  is  its  peculiarity. 

The  electric  pile  of  Zamboni  is  an  example  of  the  other 
kind.  It  consists  of  a series  often  or  twenty  thousand  discs 
of  gilt  paper,  alternating  with  similar  pieces  of  very  thin 
zinc  foil.  These  are  arranged  in  a tube,  and  kept  in  contact 
by  the  pressure  of  screws  at  each  end.  In  Fig.  123,  the 
pile  is  laid  on  a pair  of  gold 
leaf  electroscopes,  both  of 
which  diverge,  the  one  be- 
ing positive  and  the  other 
negative,  the  central  parts 
of  the  pile  being  neutral. 

This  instrument  exhibits  no 
calorific  effects ; its  phe- 
nomena are  those  of  elec- 
tricity of  high  tension. 

These,  and,  indeed,  many 
of  the  phenomena  of  the 
electric  current,  are  clearly 
accounted  for  by  the  aid  of  Ohm’s  theory  of  the  Voltaic  pile, 
of  which  the  following  is  an  exposition  : 

1st.  By  ELECTRO-MOTIVE  FORCE  we  Understand  the  causes 
which  give  rise  to  the  electric  current ; this,  as  we  have  ex- 
plained in  the  simple  circle,  is  the  oxydation  of  the  zinc. 
2d.  By  RESISTANCE  we  mean  the  obstacles  which  the  cur- 
rent has  to  encounter  in  the  bodies  through  which  it  passes. 

When  we  affect  the  electric  current  in  any  portion  of  its 
path,  either  by  varying  thp  electro-motive  force,  or  changing 
the  resistances,  we  simultaneously  affect  it  throughout  the 
whole  circuit ; so  that,  in  a given  space  of  time,  the  same 
quantity  of  electricity  passes  through  each  transverse  section 
of  the  circuit. 

In  any  Voltaic  circle,  simple  or  compound,  the  force  of  the 
current  is  directly  proportional  to  the  sum  of  all  the  electro- 
motive forces  which  are  in  activity,  and  inversely  propor- 
tional to  the  sum  of  all  the  resistances ; that  is  to  say,  the 
force  of  any  Voltaic  current  is  equal  to  the  sum  of  all  the 

What  does  Zamboni’s  pile  illustrate  ? What  is  the  effect  produced  by  a 
battery  of  large  plates  1 What  by  one  of  many  alternations  1 What  is  meant 
by  electro-motive  force  ? In  a simple  circle,  what  is  its  origin  ? What  is 
meant  by  resistance  ? On  affecting  one  part  of  a current,  is  the  rest  affect- 
ed ? What  conclusion  is  draw^n  from  that  fact  ? What  is  the  force  of  the 
current  equaf  to  ? 


Fig.  123. 


140  ohm’s  theory. 

electro-motive  forces,  divided  by  the  sum  of  all  the  resist- 
ances. 

The  resistance  to  conduction  of  a metal  wire  is  directly 
as  its  length,  and  inversely  as  its  section  ; that  is  to  say,  the 
longer  the  wire  is,  the  greater  its  resistance,  and  the  thicker 
it  is,  the  less  its  resistance. 

If  we  augment  or  diminish,  in  the  same  proportion,  the 
electro-motive  forces  and  the  resistances  of  a Voltaic  circuit, 
the  force  of  the  current  will  remain  the  same ; if  we  in- 
crease the  electro-motive  force,  the  force  of  the  current  in- 
creases ; if  we  increase  the  resistance,  the  force  of  the  cur- 
rent diminishes. 

If,  in  two  Voltaic  circles  of  equal  force,  the  same  resist- 
ance is  introduced,  the  forces  of  the  currents  may  he  enfee- 
bled in  very  different  proportions  ; for  the  newly-introduced 
resistance  may,  in  one  of  the  circles,  bear  a very  great  pro- 
portion to  the  resistances  already  existing,  and,  in  the  other, 
a very  insignificant  proportion. 

The  following,  therefore,  is  the  general  law  which  de- 
termines the  force  of  a Voltaic  circuit. 

1st.  The  electro-motive  force  varies  with  the  number  of 
the  elements,  the  nature  of  the  metals,  and  of  the  liquids 
which  constitute  each  element ; but  it  does  not  in  any  man- 
ner depend  on  the  dimensions  of  their  parts. 

2d.  The  resistance  of  each  element  of  a Voltaic  circuit  is 
directly  proportional  to  the  distance  between  the  plates,  as 
occupied  by  the  liquid,  the  resistance  of  the  liquid  itself,  and 
the  length  of  the  polar  wire  connecting  the  ends  of  the  cir- 
cuit ; and  inversely  proportional  to  the  surface  of  the  plates 
in  contact  with  the  liquid,  and  to  the  section  of  the  connect- 
ing wire. 

3d.  The  force  of  the  current  is  equal  to  the  electro-mo- 
tive force  divided  by  the  resistance. 

From  the  circumstance  that  lightning  has  been  repeatedly 
known  to  render  implements  of  steel  magnetic,  and  from  a 
general  analogy  which  exists  between  the  phenomena  of 
magnetism  and  those  of  electricity,  it  was  long  ago  believed 
that  these  phenomena  were  due  to  one  common  cause  ; but 


In  a wire,  w'hat  is  the  law  of  resistance  ? How  does  the  force  of  the  cur- 
rent change  with  changes  in  the  electro-motive  force  and  the  resistance? 
When  a new  resistance  is  introduced  into  two  circles,  does  it  follow  that 
both  will  be  affected  alike  ? Give  the  general  law  which  determines  the 
force  of  the  Voltaic  current. 


MAGNETISM. 


141 


it  was  not  until  1819  that  their  true  relationship  v/as  first 
established  by  (Ersted. 

The  phenomena  of  the  magnet  itself  were  discovered  more 
than  2000  years  ago.  The  natural  magnet,  or  loadstone, 
which  is  an  iron  ore,  possesses  the  quality  of  attracting  pieces 
of  iron  or  steel,  but  upon  almost  all  other  substances  it  is 
Avithout  action.  To  hardened  steel  it  communicates  its  own 
properties  in  a permanent  manner ; but  soft  iron  is  only  tran- 
siently magnetic,  and  as  soon  as  it  is  removed  from  the  in- 
fluence of  the  magnet  it  loses  its  power.  Bars  of  steel  which 
have  been  magnetized  can  communicate  their  activity  to 
other  bars ; they  are,  therefore,  of  constant  use  in  physical 
investigations,  and  are  of  two  forms,  straight  bars  and  horse- 
shoe magnets. 

If  a magnetic  bar  have  iron  fil- 
ings sifted  over  it,  they  collect,  as 
represented  in  Fig.  124,  chiefly 
at  the  two  extremities,  cl  d,  few  of  them  being  found  in  the 
middle.  If  a piece  of 
card-board  is  laid  over 
a magnet,  and  the  fil- 
ings dusted  on  it,  they 
arrange  themselves  in 
curves,  called  magnet- 
ic curves ; there  being 
in  this,  as  in  the  for- 
mer instance,  centers 
of  action,  P P,  toward 
the  extremities  of  the 
bars,  around  which  the  curves  are  arranged.  The  appear- 
ance is  shoAvn  in  Fig.  125. 

A light  magnetic  bar,  S N,  c 

so  arranged  that  it  can  be  ^ j] 

poised  on  a pivot,  C,  with 

freedom  of  motion,  is  a mag-  I 

netic  needle.  It  was  discov-  I 

ered  by  the  Chinese  that  such  j 

a needle,  Fig.  126,  possesses 

polarity,  or  points  north  and 

What  are  the  properties  of  a magnet?  What  is  the  difference  of  its  action 
on  iron  and  steel  ? What  are  the  forms  of  artificial  magnets  ? How  may 
the  existence  of  poles  be  sho\Mi  by  iron  filings  ? Describe  a magnetic  nee- 
dle. . What  is  meant  by  its  polarity  ? 


Fisr.  124. 


142 


ELECTRO-MAGNETISM, 


south,  a fact  of  the  utmost  importance  in  navigation.  When 
to  a needle  the  poles  of  a bar  are  approached,  it  exhibits  at- 
tractive and  repulsive  movements.  The  law  under  which 
these  take  place  is,  “ Like  poles  repel,  and  unlike  ones  at- 
tract two  north  or  two  south  poles  repel,  hut  a north  and 
a south  attract.  Either  pole  of  a magnet  is  attracted  by  a 
piece  of  unmagnetized  soft  iron.  The  intensity  of  magnetic 
action  is  inversely  proportional  to  the  square  of  the  distances. 

The  north  and  south  polarities  can  not  be  isolated  from  one 

another.  If  we  take  a 
long  magnet,  JST  S,  Fig. 
127,  and  break  it  in  two, 
we  shall  not  insulate  the 
north  polarity  in  one  half 
and  the  south  in  the 


2sr' 


IQ- 

Fig.  127. 

S 

1 ^ 

s'  "N" 

S' 

1 ^ -_i 

other,  but  each  of  the  broken  magnets  will  be  perfect  in  it- 
self, having  two  poles — one  fragment  being  N'  S',  and  the 
other  N"  S". 

Of  Electro-Magnetism. 

If  a magnetic  needle  be  brought  into  the  neighborhood 
Fig.  128.  of  a wire  along  which  an  electric  cur- 

A rent  is  passing,  the  needle  is  at  once 

disturbed  from  its  position,  and  tends 
to  set  itself  at  right  angles  to  the  wire. 
Thus,  if  there  be  an  electric  current 
moving  in  the  direction  A B in  a wire, 
and  directly  over  the  wire,  and  par- 
allel to  it,  there  be  a suspended  nee- 
dle, as  soon  as  the  current  passes  the 
needle  is  deflected  from  its  position, 
and  if  the  current  is  sufficiently  pow- 
erful, comes  at  right  angles  to  the 
wire.  The  direction  in  which  the 
transverse  movement  takes  place  de- 
pends on  the  relative  position  of  the 
needle  and  the  wire : thus,  1st,  if  the  wire  be  above  the 
needle  and  parallel  to  it,  that  pole  next  the  negative  end 
of  the  battery  moves  westward  ; 2d,  if  the  wire  be  beneath 
the  needle,  it  will  move  eastward  ; 3d,  if  the  wire  be  on 

What  is  the  law  of  magnetic  attractions  and  repulsions  ? How  does  the 
intensity  of  magnetic  action  vary  ? What  is  the  direction  in  which  the  nee- 
dle mpves  in  the  four  positions  round  the  wire  ? 


ELECTRO-MAGNETISM. 


143 


the  east  side  of  the  needle,  the  pole  is  elevated  ; 4th,  if  on 
the  west,  it  is  depressed  : in  all  these  various  positions,  the 
tendency  being  to  bring  the  needle  at  right  angles,  or  trans- 
verse to  the  wire. 

It  follows,  from  these 
facts,  that  if  a magnetic 


lacts,  tnat  ii  a magnetic  ^ 
needle  be  placed  in  the  \ 
interior  of  a rectangle  of 


Fis^.  129. 


wire.  Fig.  129,  through 
which  a current  is  made 
to  flow,  all  the  portions 
of  the  wire  conspire  to 
move  the  needle  in  the 
same  direction.  The  effect,  therefore,  becomes  much  greater 
than  in  the  case  of  a single  continuous  wire. 

On  the  same  principle,  if,  instead  of  a single  turn,  the 
wire  is  repeatedly  coiled  upon  it-  Fig.  130. 

self,  as  at  a d d a,  Fig.  130,  so 
as  to  make  a great  many  turns, 
the  effect  upon  the  included 
needle,  n s,  is  greatly  increased, 
and  when  the  needle  is  made  nearly  astatic,  that  is  to  say, 
its  tendency  to  point  north  nearly  destroyed  by  arranging  it 


Fig.  131. 


upon  an  axis  with  another  needle  sim- 
ilar to  it  in  all  respects,  but  with  its 
poles  reversed,  as  N S,  S S,  Fig.  131, 
the  directive  tendency  of  the  one  nee- 
dle neutralizing  the  other,  but  both 
tending  to  turn  in  the  same  direction 
by  the  current  in  the  coil  of  wire,  in- 
asmuch as  one  is  within  the  coil  and 
the  other  above  it,  the  arrangement 
forms  a most  delicate  means  of  dis- 
covering and  measuring  an  electric 
current.  It  is  called  a galvanometer. 

As  action  and  reaction  are  always 
equal  and  contrary,  it  is  obvious  that 
if  a conducting  wire  be  movable  and 
the  magnet  stationary,  the  latter  can 
be  made  to  impress  motions  on  the  former. 

What  is  the  effect  on  a needle  in  the  interior  of  a rectangle  ? What  is 
the  principle  of  the  galvanometer?  On  the  same  j rinci];!  can  ihc  wire 
be  made  to  move  ? 


144 


ELECTRO-MAGNETIC  ROTATION. 


Fig.  133. 


Conducting  wires  can  be  made  to  revolve  round  the  poles 
of  a magnet,  or  the  pole  of  a magnet  round 
a conducting  wire  ; thus,  in  a glass  cup, 
Fig.  132,  let  a magnet,  n,  be  fixed  verti- 
cally, and  the  cup  filled  with  mercury  ; by 
means  of  a loop,  a,  let  a conducting  wire, 
b,  be  suspended,  having  perfect  freedom  of 
motion.  If  an  electric  current  is  made  to 
pass  down  this  wire  through  the  mercury, 
and  escape  by  the  path  d,  the  wire  rotates 
round  the  pole  n as  long  as  the  current 
passes.  From  this  and  similar  experi- 
ments, it  therefore  appears  that  the  force 
exerted  between  a conducting  wire  and  a magnet  is  not  a 
direct  attractive  or  repulsive  power,  but  one  continually 
tending  to  turn  the  movable  body  round 
the  stationary  one,  deflecting  it  continual- 
ly, and  acting  in  a tangential  direction. 
Hence  it  is  sometimes  spoken  of  as  a tan- 
gential force. 

If  round  a bar  of  soft  iron  a conduct- 
ing wire,  covered  over  with  silk,  be  spi- 
rally twisted,  as  in  Fig.  133,  whenever 
an  electric  current  is  passed,  the  iron  be- 
comes intensely  magnetic,  and  loses  its  mag- 
netism as  soon  as  the  current  stops.  A bar 
an  inch  in  diameter,  bent  so  as  to  represent 
a horseshoe,  Fig.  134,  with  a wire  covered 
with  silk  for  the  purpose  of  separating  its 
successive  strands  from  each  other,  may  be 
made  to  give  rise  to  very  striking  results. 
Professor  Henry,  by  a modification  of  the  con- 
ducting wire,  succeeded  in  imparting  so  in- 
tense a degree  of  magnetism  to  a piece  of 
soft  iron  that  it  could  support  more  than  a 
ton  weight.  If  under  one  of  these  electro- 
magnets a dishful  of  small  iron  nails  be  held, 
the  moment  the  current  passes,  the  nails  are 
all  attracted,  and,  while  they  are  held  by 


Fig.  134. 


Describe  a method  of  showing  the  rotation  of  a wire  round  the  pole  of  a 
magnet.  What  is  the  nature  of  the  force  exerted  between  a conducting  wire 
and  a magnet?  Describe  the  construction  and  properties  of  a straight 
electro-magnet.  Describe  the  horseshoe  clefctro-magnet. 


MAGNETIC  AND  DIAMAGNETIC  BODIES. 


145 


its  poles,  may  be  moulded,  as  it  were,  by  the  hand  in  vari- 
ous shapes,  but  as  soon  as  the  current  stops  they  fall  off. 

It  is  upon  this  principle  of  producing  temporary  magnet- 
ism by  an  electric  current  that  Morse’s  electric  telegraph 
depends. 

When  different  substances  are  suspended  between  the 
polar  terminations  of  one  of  these  horseshoe  electro-magnets 
— in  the  magnetic  field,  as  it  is  termed — it  is  found  that 
some  arrange  themselves  from  pole  to  pole,  and  others  trans- 
versely to  that  position ; the  former  are  called  magnetic  and 
the  latter  diamagnetic  bodies  : 


Magnetic  Bodies. 

Iron, 

Nickel, 

Cobalt, 

Platinum, 

Palladium, 

Titanium, 

Bottle  glass, 
Crown  glass, 

&c.,  &c. 


Diamagnetic  Bodies, 

Bismuth, 

Antimony, 

Zinc, 

Tin, 

Rock  crystal, 

Wood, 

Beef, 

Bread, 

&c.,  &c. 


Hot  air  is  more  diamagnetic  than  cold  air ; a flame,  there- 
fore, spreads  itself  transversely  in  the  magnetic  field.  In 
an  atmosphere  of  coal  gas,  oxygen  presents  the  aspect  of  a 
strongly  magnetic  body. 


LECTURE  XXXIII. 

Electro  - dynamics  — Thermo  - electricity,  &c.  — Am- 
ferds  Discovery. — Properties  of  a Helix. — Nature  of 
the  Magnet. — Faraday's  Discovery  of  Magnetic  Elec- 
tricity.— Magnetic  Machines. — Faradian  Currents. — 
Thermo-electricity. — Production  of  Heat  and  Cold  by 
Electric  Currents. — Thermo-electric  Pairs. — Peculi- 
arity of  these  Currents. — Electro-motive  Power  of  Heat. 
— Melloni's  Pile  and  Thermometer. — Improvements  in 
Thermo-electric  Pairs. — Animal  Electricity. — Steam 
Electricity. 

Soon  after  the  relation  between  electrieity  and  magnet- 
i.sm  was  established,  M.  Ampere  discovered  that  there  are 
reactions  between  electric  currents  themselves. 


What  are  magnetic  and  diamagnetic  bodies  X 

G 


146 


PROPERTIES  OF  A HELIX. 


Fig.  136. 


Two  electric  currents  flowing  in  the  same  direction  at- 
tract each  other,  but  two  electric  currents  flowing  in  oppo- 
Fig.  135.  site  directions  repel ; or,  more  briefly,  ‘ ‘ Like 
currents  attract,  and  unlike  ones  repel.” 
If  a conducting  wire  be  bent  in  the  form 
of  a helix,  its  terminations  returning  to- 
ward its  middle,  as  shown  in  Fig.  135,  it 
exhibits  all  the  properties  of  an  ordinary 
magnetized  bar ; for,  as  soon  as  the  current 
passes,  it  points  north  and  south,  and  is 
attracted  and  repelled  by  the  poles  of  a 
magnet  lust  as  though  it  were  a magnet 
itself.  A very  neat  arrangement  for  illus- 
trating these  results  is  seen  in  Fig.  136.  A small  simple 
circle,  consisting  of  a zinc  and  cop- 
per plate,  connected  together  by 
means  of  a wire  bent  so  as  to  form 
a flat  coil,  is  floated  by  means  of 
a cork  in  acidulated  water.  The 
current  runs  round  the  coil  in  the 
direction  of  the  arrows,  and  the 
arrangement,  obeying  the  mag- 
netic influence  of  the  earth,  turns, 
with  its  plane  pointing  north  and 
south,  just  as  a magnet  would  do 
if  introduced  into  the  interior  of 
the  coil,  in  the  position  shown  in 
the  figure  by  the  dark  line. 

Ampere  infers,  from  the  analogy  of  these  instruments, 
that  the  magnet  owes  its  qualities  to  electric  currents  cir- 
culating in  it  in  a transverse  direction.  The  directive  ac- 
tion of  the  magnetic  needle  or  the  electric  helix  depends 
on  the  reaction  of  electric  currents  circulating  in  the  earth, 
due  to  the  unequal  heating  of  its  surface  by  the  rays  of 
the  sun. 

"We  have  seen  that  an  electric  current  can  develop  mag- 
netism in  a bar  of  iron  or  steel ; in  the  former,  transient, 
in  the  latter,  permanent  magnetism.  Thus,  if  the  iron  bar, 
n s.  Fig.  137,  be  placed  in  the  axis  of  a helix  of  copper 
wire,  along  which  a current  is  flowing,  the  current  develops 

What  is  the  law  of  reaction  between  electric  currents  ? Describe  the 
phenomena  of  the  electro-dynamic  helix,  Fig.  135.  Describe  those  of  the 
flat  coil.  What  is  Ampere’s  theory  of  the  nature  of  the  magnet  ? 


MAGNETO-ELECTRIC  CURRENTS. 


147 


magnetism  in  the  bar.  It 
was  discovered  by  Faraday 
that  the  converse  also  holds 
good,  and  that  a magnet  can 
give  rise  to  an  electric  cur- 
rent. Thus,  in  Fig.  137,  let 
the  terminations  a b oi  the  helix  c be  brought  in  contact, 
and  having  placed  a soft  iron  bar,  n s,  within  it,  let  the  bar 
be  made  magnetic  by  the  approach  of  a strong  magnet.  As 
n s assumes  the  magnetic  condition,  it  generates  a current, 
which  runs  through  the  helix  c ; and  if  at  this  moment  the 
wires  a h are  drawn  apart,  a bright  spark,  sometimes  called 
the  magnetic  spark,  passes.  It  does  not  come,  however,  from 
the  magnet  itself,  but  is  due  to  the  electric  current  estab- 
lished in  the  helix  by  the  disturbing  action  of  the  magnet. 
If  between  the  terminations  a 6 a slender  wire  is  placed,  it 
may  be  made  red-hot,  or  water  may  be  decomposed,  or  any 
of  the  phenomena  of  a Voltaic  battery  may  be  exhibited  by 
the  aid  of  this  magneto-electric  current.  On  this  principle 
are  constructed  the  magneto-electric  machines,  of  which 
different  foims  have  of  late  been  so  generally  introduced  for 
the  purpose  of  the  medicinal  application  of  electricity.  They 
all  depend  essentially  on  the  principle,  that  if  we  coil  round 
a piece  of  soft  iron  a conducting  wire,  as  often  as  the  iron 
is  magnetized  a wave  of  electricity  flows  through  the  wire. 

If  two  conducting  wires  be  placed  parallel  and  near  to 
each  other,  when  an  electric  current  is  passed  through  one 
of  them  a wave  of  electricity  flows  in  the  opposite  direction 
through  the  other  ; and  on  the  first  current  stopping,  another 
wave,  coinciding  with  it,  passes  through  the  second  wire. 
These  momentary  currents  are  all  called,  from  Fi^.idS. 
the  name  of  their  discoverer,  Faradian  currents. 

If  we  take  a bar  of  antimony,  a,  Fig.  138, 
and  one  of  bismuth,  5,  and  having  soldered 
them  end  to  end  at  c,  pass  a feeble  current 
through  them  in  a direction  from  the  antimony 
to  the  bismuth,  the  temperature  of  the  com- 
pound bar  rises ; but  if  the  current  passes  in 
the  opposite  direction,  cold  is  produced.  By 

Can  a magnetized  bar  be  made  to  develop  electric  currents  ? What  are 
the  properties  of  these  currents  ? What  is  the  principle  of  the  magneto- 
electric machine  ? What  is  meant  by  Faradian  currents  ? What  is  their 
direction  ? IIow  may  heat  and  cold  be  produced  by  a current  in  a com- 
pound bar  ^ 


148 


THERMO-ELECTRIC  CURRENTS. 


fixing  thermometers  into  the  substance  of  the  bars,  these 
facts  may  be  readily  verified,  and  in  the  latter  case,  when 
water  is  placed  in  a depression  made  for  it  in  the  bar,  and 
the  reduction  of  temperature  slightly  aided,  it  can  be  frozen 
by  the  electric  current. 

The  same  compound  bar  of  bismuth  and  antimony,  hav- 
ing its  extremities  connected  together  by  a wire,  whenever 
heat  is  applied  to  the  junction,  an  electric  current  sets  from 
the  bismuth  to  the  antimony,  and  when  cold  is  applied,  from 
the  antimony  to  the  bismuth.  These  important  facts  were 
discovered  by  Seebeck  in  1822,  and  the  currents  have  been 
designated  by  him  thermo-electric  currents. 

For  the  production  of  these  thermo-electric  effects,  two 
metals  are  not  necessarily  required.  One  end  of  a thick 
metallic  wire  being  made  red  hot  and  brought  in  contact 
with  the  other,  a current  instantly  passes  from  the  hot  to 
the  colder  portion,  and  continues  to  flow  in  diminishing 
quantities  until  the  two  ends  have  reached  the  same  tem- 
perature. Or  if  a metallic  ring  be  made  red  hot  in  any 
limited  portion  of  its  circumference,  so  long  as  the  heat 
passes  with  freedom  to  the  right  hand  and  to  the  left,  elec- 
tric development  does  not  appear ; but  if  we  touch  with  a 
cold  rod  the  hot  portion,  abstracting  thereby  a portion  of  its 
heat,  a current  in  an  instant  runs  round  it. 

It  is  not  alone  in  metals  that  these  thermo-electric  cur- 
rents can  be  induced ; other  solids,  and  even  liquids,  may 
originate  them.  Among  metals  associated  together,  the 
relation  often  exhibits  singular  changes.  Copper  and  iron 
form  a very  active  couple  until  their  temperature  approaches 
800°  F.  ; the  current  then  stops,  and  on  continuing  the 
heat,  another  current  is  developed,  passing  in  the  opposite 
way.  The  same  takes  place  with  a pair  of  silver  and  zinc, 
at  a temperature  of  248°  F. 

Thermo-electric  currents  generated  in  metallic  bars,  ex- 
periencing little  resistance  to  conduction,  have  therefore 
very  little  tension  ; the  thinnest  stratum  of  water  is  a per- 
fect non-conductor  to  them. 

In  any  thermo-electric  couple,  the  quantity  of  electricity 
evolved  depends  upon  the  temperature ; but,  as  I have 


What  are  thermo-electric  currents  ? Can  they  be  generated  by  one  metal 
only?  Can  they  originate  in  other  solids  besides  metals,  and  in  liquids? 
What  is  the  action  of  a pair  of  copper  and  iron,  and  silver  and  zinc?  Why 
have  they  so  little  tension  ? 


THE  THERMO-ELECTRIC  MULTIPLIER. 


149 


shown  in  a memoir  on  the  electro-motive  power  of  heat,  in- 
serted in  the  Philosophical  Magazine  for  June,  1840,  it  is 
not  directly  proportional  to  it,  except  through  limited  ranges 
of  temperature  ; we  can  not,  therefore,  make  use  of  these 
currents  for  the  determination  of  temperatures  with  accu- 
racy, on  the  hypothesis  of  the  proportionality  of  the  quanti; 
ties  of  electricity  to  the  quantities  of  heat. 

By  joining  a system  of  bars  alternately  together,  we  may 
reduplicate  the  effects  of  a single  pair.  As  might  have 
been  predicted  on  the  theory  of  Ohm,  and  as  I have  shown 
in  the  memoir  just  quoted  experimentally,  where  the  con- 
ducting resistance  remains  the  same,  the  quantity  that 
passes  the  circuit  is  directly  proportional  to  the  number  of 
pairs.  It  is  upon  this  principle  that,  several  years  ago,  M. 
Mellon!  constructed  his  thermo-electric  multiplier.  Fig,  139. 


Fig,  139. 


Thirty  or  forty  pairs  of  minute  bars  of  bismuth  and  anti- 
mony, F F,  with  their  alternate  ends  soldered  together,  are 
arranged  in  a small  space,  so  that  their  ends  expose  an 
area  not  exceeding  the  section  of  the  bulb  of  a common  ther- 
mometer, the  current  that  passes  from  this  pile  being  so 
conducted,  by  means  of  wires,  C C,  as  to  deflect  a magnetic 
needle.  To  the  thermo-electric  pile  a galvanometer  is  there- 
fore attached,  as  seen  in  Fig.  140,  which  represents  the 
whole  instrument  in  section  and  perspective.  A B C is  the 
coil  of  the  multiplier,  its  terminal  wires  ending  in  the  con- 
necting cups,  F F'.  The  coil  rests  on  a plate,  D E,  which 
can  be  made  to  revolve  by  means  of  a wheel  and  screw  con- 
nected with  the  button  G.  An  astatic  combination  of  nee- 
dles is  supported  by  the  frame  Q;  M N,  by  a single  silk 
thread,  V L.  To  protect  the  instrument  from  currents  of 
air,  it  is  covered  with  a glass  cylinder,  F L,  strengthened 
by  brass  rings,  P S,  Y Z ; K T is  the  basis  on  which  the 
cylinder  rests.  The  angle  of  deflection  of  the  needle  is 


Is  the  quantity  of  electricity  evolved  proportional  to  ihe  temperature? 
What  is  the  principle  of  the  ihermo-electrio  multiplier  of  Melloni  ? How 
is  it  constructed  ? 


150 


THERMO-ELECTRIC  PAIRS. 


Fig.  140. 


Fig.  141, 


>vvv 

1 c 

b a 

A/ 

h' 

m 

u 


taken  as  the  measure  of  the  temperature.  Of  all  thermom- 
eters, this  is  by  far  the  most  sensitive. 

I have  introduced  certain  improvements  in  the  construc- 
tion of  the  thermo-elec- 
tric element.  Let  a, 
Fig.  141 , be  a bar  of  an- 
timony, and  5 a bar  of 
bismuth.  Let  them  be 
soldered  along  c cl,  and 
at  cl  let  the  temperature 
be  raised  ; a current  is 
immediately  excited,  but 
this  does  not  pass  round 
the  bars  a 5,  inasmuch 
as  it  finds  a shorter  and  readier  channel  through  the  metals 
between  c and  d,  as  indicated  by  the  arrows.  Nor  will 
the  whole  current  pass  round  the  bars  until  the  temperature 
of  the  soldered  surface  has  become  uniform.  An  improve- 
ment on  this  construction  is,  therefore,  such  as  is  represent- 
ed at  a'  y , v/hich  consists  of  the  former  arrangement  cut 
out  along  the  dotted  lines  ; here  the  whole  current,  as  soon 
In  what  manner  may  the  simple  thermo-electric  pair  be  improved  ? 


ANIMAL  ELECTRICITY. 


151 


as  it  exists,  is  forced  to  pass  along  the  bars.  One  of  the  best 
forms  of  a thermo-electric  pair  is  given  at  5'',  where  a" 
is  a semi-cylindrical  bar  of  antimony  and  5"  of  bismuth, 
united  by  the  opposite  corners  of  a lozenge-shaped  piece  of 
copper,  c.  The  heat  is  to  fall  on  c,  which  becomes  hot  and 
cold  with  promptitude,  and  determines  a current. 

Besides  the  various  sources  of  electricity  to  which  I have 
referred,  there  are  certain  animals  which  possess  the  power 
of  controlling  the  equilibrium  of  the  electric  fluid  in  their 
neighborhood  at  will,  being  accommodated  for  this  purpose 
with  a specific  nervous  apparatus.  The  torpedo,  a fish 
living  in  the  Mediterranean,  and  the  gymnotus  electricus, 
which  is  found  in  some  of  the  fresh  water  streams  of  South 
America,  have  this  property.  The  shock  of  the  torpedo 
passes  through  conducting  bodies,  but  not  through  non-con- 
ductors. A gymnotus  which  was  exhibited  in  London  was 
found  to  deflect  a magnetic  needle  powerfully  by  its  dis- 
charge. A steel  wire  was  magnetized  by  it,  and  iodide  of 
potassium  decomposed.  In  an  interrupted  metallic  circuit 
a spark  was  seen,  and  the  induced  spark  was  also  obtained 
by  a coil.  The  current  passed  from  the  anterior  to  the  pos- 
terior parts  of  the  animal.  Mr.  Faraday,  the  author  of 
these  experiments,  calculates  that  the  quality  of  electricity 
passing  at  each  discharge  of  the  fish  was  equal  to  that  of  a 
Leyden  battery  containing  3500  square  inches  charged  to 
its  highest  degree,  and  this  could  be  repeated  two  or  three 
times  with  scarce  a sensible  interval  of  time. 

As  the  electricity  which  these  animals  discharge  depends 
on  their  nervous  action,  the  production  of  it  is  attended  with 
a corresponding  nervous  exhaustion.  It  is,  therefore,  not 
improbable  that  the  converse  of  these  actions  holds  good, 
and  hereafter  it  will  be  found  that  electricity  reacts  on  the 
nervous  fluid. 

It  has  been  shown  by  Matteucci  that  in  all  living  ani- 
mals there  is  a current  of  positive  electricity  from  the  in- 
terior to  the  exterior  of  every  muscle,  and  by  arranging  a 
series  of  muscles  in  such  a way  as  to  form  a pile,  magnetic 
effects  and  chemical  decomposition  may  be  produced. 

In  concluding  this  subject,  I may  mention  a source  of 

What  is  animal  electricity?  By  what  animals  is  it  exhibited?  What 
effects  have  been  produced  by  the  electricity  of  the  gymnotus  ? What  is 
the  computed  quantity  of  the  electricity  in  each  discharge  ? Why  is  this 
electric  development  attended  with  a nervous  exhaustion?  What  is  the 
direction  of  the  muscular  current  ? 


152  ELECTRICITY  PRODUCED  BY  STEAM. 

electricity  which  of  late  has  excited  much  attention.  When 
high-pressure  steam  is  allowed  to  escape  from  a boiler 
through  a narrow  jet,  a powerful  excitement  is  produced, 
and  sparks  many  feet  in  length  may  he  obtained.  The 
effect  appears  to  be  due  to  the  friction  of  minute  drops  of 
water  against  the  tube  through  which  the  steam  is  escaping. 


What  is  the  cause  of  electricity  produced  by  steam  ? 


PART  II. 


LECTURE  XXXIV. 

The  Nomenclature. — The  French  Nomenclature. — Ta 
hie  of  Elementary  Bodies. — Nomenclature  for  Com 
pou7id  Bodies,  Adds,  Bases,  and  Salts. 

Until  after  the  discovery  of  oxygen  gas,  the  nomencla- 
ture of  chemistry  was  very  loose  and  complicated.  The 
trivial  names  which  were  bestowed  on  various  bodies  had 
frequently  little  connection  with  their  properties ; sometimes 
they  were  derived  from  the  name  of  the  discoverer,  or  some- 
times from  the  place  of  his  residence.  Glauber  salt  takes 
its  designation  from  the  chemist  who  first  brought  it  into 
notice,  and  Epsom  salt  from  a village  in  England,  in  which 
it  was  at  one  time  made. 

It  is  obvious  that  such  a system  of  nomenclature,  as  soon 
as  the  number  of  compound  bodies  increased,  would  not  only 
become  unmanageable,  but,  by  reason  of  the  impossibility 
of  carrying  in  the  memory  such  a mass  of  unconnected  terms, 
offer  a very  serious  impediment  to  the  progress  of  the  science. 
Lavoisier  and  his  associates,  about  the  close  of  the  last  cen- 
tury, constructed  a new  nomenclature,  with  a view  of  avoid- 
ing these  difficulties.  Its  principles,  with  some  modifica- 
tions, are  now  universally  received.  The  following  is  a 
brief  exposition  of  it : 

Natural  bodies  may  he  divided  into  two  classes,  simple 
and  compound  ; the  former  are  also  called  elementary.  By 
simple  or  elementary  bodies  we  mean  those  which  have  not 
as  yet  been  decomposed. 

Among  simple  substances,  those  which  have  been  known 
for  a long  time  retain  the  names  by  which  they  are  popu- 
larly distinguished ; thus,  gold,  iron,  copper,  &c.  ; and  when 


What  was  the  nature  of  the  nomenclature  used  by  the  older  chemists? 
When  was  the  system  now  in  use  invented  ? What  is  meant  by  simple  or 
elementary  bodies  ? What  is  the  rule  for  the  old  simple  bodies  ? 

G 2 


154 


NOMENCLATURE  FOR  SIMPLE  BODIES. 


new  bodies  belonging  to  this  class  are  discovered,  they  are 
to  receive  a name  descriptive  of  one  of  their  leading  prop* 
erties  ; thus,  chlorine  takes  its  name  from  its  greenish  color, 
and  iodine  from  its  purple  vapor.  It  is  to  be  regretted  that 
this  rule  has  often  bee:i  overlooked. 

Some  doubt  exists  as  to  the  exact  number  of  the  ele- 
mentary bodies.  It  may  be  estimated  at  62,  including 
three  metals  recently  discovered,  the  titles  of  which  have 
not  yet  been  completely  established. 

Of  the  list  of  elementary  bodies,  the  metals  form  by  far  the 
larger  portion,  there  being  49  of  them ; the  remaining  13  are 
commonly  spoken  of  as  non-metallic  substances.  By  some 
authors  these  are  called  metalloids,  in  contra-distinction  to 
the  metals,  an  epithet  which,  however,  is  very  objectionable. 


Table  of  elementary  or  simple  Substances,  with  their  Sym- 
bols and  Atomic  Weights. 


Non-metallic  Elements. 

Symbols. 

At.  wts. 

Metallic  Elements. 

Symbols. 

At.  wts. 

Oxygen  . . 

0. 

8-013 

Erbium  .... 

E. 

— 

Hydrogen  . 

H. 

1-000 

Terbium  . . . 

Tr. 

— : — 

Nitrogen  . 

N. 

14-19 

Manganese  ‘ . . 

Mn. 

27-72 

Sulphur . . 

S. 

16-12 

Iron 

Fe. 

27-18 

Phosphorus 

P. 

32-00 

Cobalt  .... 

Co. 

29-57 

Carbon  . . 

c. 

6*04 

Nickel  .... 

Ni. 

29-62 

Chlorine 

Cl. 

35-47 

Zinc 

Zn. 

3231 

Bromine 

Br. 

78-39 

Cadmium  . . . 

Cd. 

55-83 

Iodine  . . 

I. 

126-57 

Lead 

Pb. 

103-73 

Fluorine 

F. 

18-74 

Tin 

Sn. 

58-92 

Boron  . . 

B. 

10-91 

Bismuth  ... 

Bi. 

71-07 

Silicon  . . 

Si. 

22-22 

Copper  .... 

Cu. 

31-71 

Selenium  . 

Se. 

39*63 

Uranium  ... 

U. 

217-20 

Mercury  . . . 

Hg. 

202-87 

Metallic  Elements. 

Silver  .... 

Ag. 

108-31 

Potassium  . 

K. 

39-26 

Palladium  . . . 

Pd. 

53-36 

Sodium  . . 

Na. 

23-31 

Rhodium  . . . 

R. 

52-20 

Lithium . . 

L. 

6-44 

Iridium  .... 

Ir. 

98-84 

Barium  . . 

Ba. 

68-66 

Platinum  . . . 

Pt. 

98-84 

Strontium  . 

Sr. 

43-85 

Gold 

Au. 

199-2 

Calcium 

Ca. 

20-52 

Osmium  . . . 

Os. 

99-72 

Magnesium 

Mg. 

12-89 

Titanium  . . . 

Ti. 

24-33 

Aluminum  . 

Al. 

13-72 

Tantalum  . . . 

Ta. 

184-90 

Glucinura  . 

G. 

26  54 

Tellurium  . . . 

Te. 

64-25 

Yttrium . . 

Y. 

32-25 

Tungsten  . . . 

W. 

99-70 

Zirconium  . 

Z. 

33-67 

Molybdenum  . . 

Mo. 

47-96 

Thorium  . 

Th. 

59-83 

Vanadium  . . . 

V. 

68-66 

Cerium  . . 

Ce. 

46-05 

Chromium  . . . 

Cr. 

28-19 

Lanthanum 

La. 

— 

Antimony  . . . 

Sb. 

64-62 

Didymium  . 

D. 

— 

Arsenic  .... 

As. 

37-67 

What  is  the  rule  for  the  simple  bodies  newly  discovered  ? What  is  the 
number  of  the  elementary  bodies  ? Of  these,  to  what  class  do  the  greater 
part  belong  1 What  are  the  symbols  for  the  elementary  bodies  ? What  are 
their  atomic  weights  ? 


NOMENCLATURE  FOR  COMPOUNDS. 


155 


To  this  table  the  names  of  four  metals,  recently  discov- 
ered and  hut  little  known,  might  be  added.  They  are  Ni- 
obium (Nb.),  Norium  (No.),  Pelopium  (Pe.),  and  Ruthe- 
rium  (Ru.). 

Compound  bodies  may,  for  the  most  part,  he  divided  into 
three  groups  : acids,  bases,  and  salts.  By  an  acid  we  mean 
a body  having  a sour  taste,  reddening  vegetable  blue  colors, 
and  neutralizing  alkalies  ; by  a base,  a body  which  restores 
to  blue  the  color  reddened  by  an  acid,  and  possessing  the 
quality  of  neutralizing  the  properties  of  an  acid  ; by  a salt, 
the  body  arising  from  the  union  of  an  acid  and  a base 
These  definitions,  however,  are  to  be  received  with  consid 
erable  limitation. 

The  nomenclature  for  acid  substances  is  best  seen  from 
an  example.  Thus  sulphur  and  oxygen  unite  to  form  an 
acid  : it  is  called  sulphuric  acid ; the  termination  in  ic  being 
expressive  of  that  fact.  But  very  frequently  two  substances 
will  form  more  than  one  acid,  by  uniting  in  different  pro- 
portions ; in  this  ease  the  termination  in  ou^  is  used  ; thus 
we  have  sulphurous  acid,  so  called  because  it  contains  less 
oxygen  than  sulphuric.  The  prefix  “ hypo”  is  also  used, 
as  in  hyposulphurous  and  hyposulphuric  acids : it  indicates 
acids  containing  les^  oxygen  than  sulphurous  and  sulphuric 
acids.  The  prefix  “ hyper”  is  used  in  the  same  way  ; thus, 
hyperchloric  acid,  an  acid  containing  more  oxygen  than 
chloric  acid. 

"With  respect  to  bases,  the  generic  termination  is  in  ide. 
If  oxygen  and  lead  unite,  we  have  oxide  of  lead,  and  in  the 
same  manner  we  have  chlorides,  bromides,  iodides,  and  fluor- 
ides. And  if  these  elements  form  compounds  in  more  pro- 
portions than  one,  we  indicate  their  proportion  by  the  Greek 
numerals,  protos,  deuteros,  tritos  : thus  we  have  protoxides, 
deutoxides,  tritoxides  ; the  protoxide  of  lead  contains  one 
atom  of  oxygen  and  one  of  lead,  the  deutochloride  of  mer- 
cury two  atoms  of  chlorine  and  one  of  mercury,  &c.  In  the 
same  manner,  the  prefixes  sub,  sesqui,  and  per  are  used ; 
thus,  a suboxide  contains  the  lowest  proportion  of  oxygen, 
a peroxide  the  highest  proportion,  and  a sesquioxide  inter- 


Into  what  groups  may  compound  bodies  be  divided  ? What  is  the  defi- 
nition of  an  acid  ? What  is  a base  ? What  is  a salt  ? What  do  the  term- 
inations ic  and  ous  indicate  t What  is  the  meaning  of  the  prefixes  hypo  and 
hyper  ? What  does  the  termination  ide  signify  ? What  the  prefixes  protos^ 
deuteros,  and  tritos,  sub,  sesqui,  and  per  ? 


156 


METHOD  OP  SYMBOLS, 


venes  between  a protoxide  and  a deutoxide,  its  oxygen  being 
in  the  proportion  of  one  atom  and  a half. 

By  an  alloy,  we  mean  the  substance  arising  from  the 
union  of  two  metals ; thus  copper  and  zinc  unite  to  form 
brass,  which  is  an  alloy.  If  one  of  the  metals  is  mercury, 
the  compound  is  called  an  amalgam.  And  when  sulphur, 
phosphorus,  carbon,  and  selenium  unite  with  metals,  or  with 
each  other,  the  termination  uret  is  used  ; thus  we  have  sul- 
phurets,  phosphurets,  carburets,  &c. 

With  respect  to  the  nomenclature  for  salts,  the  termina- 
tions ate  and  ite  are  used  to  indicate  acids  in  and  cuts  re- 
spectively. The  sulphate  of  potash  contains  sulphuric  acid, 
.and  the  sulphite  of  potash  sulphurous  acid.  And  as  we 
have  already  seen  that  different  oxides  arise  by  the  union 
of  oxygen  in  different  proportions,  and  these  bodies  frequent- 
ly give  rise  to  different  series  of  salts,  the  operation  of  the 
nomenclature  may  be  readily  traced : thus,  the  protosul- 
phate of  iron  is  the  sulphate  of  the  protoxide  of  iron,  but  the 
persulphate  of  iron  is  a sulphate  of  the  peroxide,  and  the 
deutosulphate  of  platinum  a sulphate  of  the  deutoxide  of 
platinum.  When  the  relative  quantity  of  the  acid  and 
base  varies,  Latin  numerals  are  employed ; thus  the  bisul- 
phate of  potash  contains  two  atoms  of  sulphuric  acid  and 
one  of  potash. 

Salts  are  said  to  be  neutral  if  neither  their  acid  nor  base 
be  in  excess.  If  the  acid  predominates,  it  is  an  acid,  or 
super-salt  > if  the  base,  it  is  a basic,  or  sub-salt. 


LECTURE  XXXV. 

The  Symbols — Failure  of  the  Nomenclature  in  the  Case 
of  Com'plex  Compounds. — Failure  in  Difference  of 
Grouping. — Symbols  for  elementary  Bodies. — Expres- 
sions for  several  Atoms. — Use  of  the  Plus  Sign. — Ex- 
pressions  for  Grouping. 

So  long  as  the  constitution  of  compound  bodies  is  sim- 
ple, there  is  no  difficulty  in  applying  the  nomenclature,  or 

What  is  an  alloy  and  an  amalgam  ? When  is  the  termination  uret  em- 
ployed? What  do  the  terminations  ate  and  ite  indicate  ? What  is  the  no- 
menclature for  the  salts  ? What  is  a neutral  salt  ? What  is  an  acid,  or 
8uper-s£^lt  ? What  is  a basic,  or  sub  salt  ? 


IMPERFECTIONS  OP  THE  NOMENCLATURE.  157 


in  recognizing  from  the  name  of  the  compound  the  nature 
and  proportions, of  its  constituents.  Thus,  protoxide  of  hy- 
drogen clearly  indicates  a body  in  which  one  atom  of  oxy- 
gen is  united  with  one  of  hydrogen,  bisulphate  of  potash  a 
body  composed  of  two  atoms  of  sulphuric  acid  and  one  of 
potash,  and  even  in  more  complicated  cases,  such  as  the 
sulphato-tri  carbon  ate  of  lead,  &c.,  the  same  principle  will 
serve  as  a guide. 

But  when  compound  bodies  consist  of  a great  number 
of  atoms,  the  nomenclature  ceases  to  be  of  any  service. 
Thus,  starch  is  composed  of  twelve  atoms  of  carbon,  ten 
of  hydrogen,  and  ten  of  oxygen.  Fibrin  is  composed  of 
forty-eight  atoms  of  carbon,  thirty-six  of  hydrogen,  four- 
teen of  oxygen,  six  of  nitrogen,  with  minute  but  essential 
quantities  of  sulphur  and  phosphorus.  On  the  principles 
of  the  nomenclature,  it  would  be  difficult  to  give  to  the 
first  a technical  name,  and  in  the  case  of  the  latter  impos- 
sible. 

The  peculiarity  of  organic  compounds  is,  that  they  con- 
tain but  few  of  the  elementary  bodies,  being  chiefly  made 
up  of  carbon,  hydrogen,  oxygen,  and  nitrogen  ; but  these, 
as  in  the  case  of  fibrin,  unite  in  a very  complicated  way, 
very  often  hundreds  of  atoms  being  involved.  The  nomen- 
clature is  therefore  inapplicable  to  organic  chemistry. 

There  is  also  another  very  serious  difficulty  in  its  way. 
It  has  been  discovered  that  compounds  may  consist  of  the 
same  elements,  united  in  precisely  the  same  proportions, 
so  that  when  they  are  analyzed  they  yield  precisely  the 
same  results,  and  yet  they  may,  in  reality,  be  very  differ- 
ent substances.  Identity  in  composition  is  no  proof  of  the 
sameness  of  bodies.  Thus  we  may  have  the  same  ele- 
ments uniting  together  in  the  same  proportion,  and  yielding 
a solid,  a liquid,  or  a gas  indifferently.  This  result  may  de- 
pend on  several  causes,  as  will  be  presently  explained  ; -but 
among  these  causes  I may  here  specify  what  is  termed  by 
chemists  “ Grouping.”  Thus,  suppose  four  elementary  bod- 
ies, A B C D,  unite  together,  there  is  obviously  a series  of 
compounds  which  may  arise  by  permuting  or  grouping  them 
differently,  as  in  the  following  example  : 


Under  what  circumstances  does  the  nomenclature  apply,  and  when  does 
it  fail  ? What  is  the  peculiarity  of  organic  compounds  ? Why  is  the 
nomenclature  inapplicable  to  organic  chemistry  ? Is  identity  of  composi- 
tion any  proof  of  the  identity  of  bodies?  What  is  meant  by  grouping? 


158 


METHOD  OF  SYMBOLS. 


(1)  A + B+C  + D. 

(2)  AC  +BD. 

(3)  A D "4"  C B. 

&c.  &c. 

The  method  of  symbols,  which  is  designed  to  meet  these 
difficulties,  and  is,  in  reality,  an  appendix  and  improvement 
upon  the  nomenclature,  was  originally  introduced  by  Ber- 
zelius ; but  the  form  which  is  now  most  commonly  adopted 
is  that  of  Liebig  and  Poggendorffi  The  advantages  which 
have  been  found  to  accrue  from  it  are  so  great,  that  it  is 
now  introduced  into  every  part  of  chemistry,  so  that  it  is 
impossible  to  read  a modern  work  on  this  science  without 
having  previously  mastered  the  symbols. 

The  student  should  not  be  discouraged  at  the  mathemat- 
ical appearance  of  chemical  formula?.  He  will  find,  by  a 
little  attention,  that  they  are  founded  upon  the  simplest 
principles,  and  involve  merely  the  arithmetical  operations 
of  addition  and  multiplication.  The  following  is  a brief 
exposition  of  their  nature  : 

For  the  symbol  of  an  elementary  substance  we  take  the 
first  letter  of  its  Latin  name,  as  is  shown  in  the  table  given 
in  the  last  lecture.  Those  symbols  should  be  committed  to 
memory.  But  as  it  happens  that  several  substances  some- 
times have  the  same  initial  letter,  to  distinguish  between 
them  we  add  a second  small  letter.  Thus,  carbon  has  for 
its  symbol  C. ; chlorine.  Cl. ; copper  (cuprum),  Cu. ; cad- 
mium, Cd.,  &c.  It  may  be  observed  that  in  the  case  of 
recent  Latin  names  the  German  synonym  is  always  used ; 
thus,  potassium  is  called  kalium  in  Germany,  and  has  for 
its  symbol  K. ; sodium  is  called  natrium,  and  has  for  its 
symbol  Na.y  &c. 

But  a symbolic  letter  standing  alone  not  merely  repre- 
sents a substance ; it  farther  represents  one  atom  of  it ; thus, 
C means  one  atom  of  carbon,  and  O one  atom  of  oxygen. 

If  we  wish  to  indicate  that  more  than  one  atom  is  pres- 
ent, we  affix  an  appropriate  figure,  as  in  the  following  ex- 
amples • ^12  . . Ojo-  Thus,  nitric  acid  is  composed  of 

one  atom  of  nitrogen  united  to  five  of  oxygen,  and  we  write 
it  NO^. 

Give  an  example  of  grouping.  What  are  the  symbols  for  elementary  bod- 
ies ? When  two  bodies  begin  with  the  same  letter,  how  are  the  symbols 
arranged  ? What  does  a single  symbol  standing  alone  represent  ? How  are 
more  atoms  than  one  represented  ? 


METHOD  OP  SYMBOLS. 


159 


When  a compound,  formed  of  several  compounds,  is  to 
be  represented,  we  make  use  of  an  intervening  comma ; 
thus,  strong  oil  of  vitriol  is  composed  of  one  atom  of  sulphur 
and  three  of  oxygen,  united  with  one  atom  of  water,  which 
is  composed  of  one  atom  of  oxygen  and  one  of  hydrogen,  and. 
we  write  it  SO^,  HO. 

If  we  desire  to  indicate  that  compounds  are  united  with 
a feeble  affinity,  we  make  use  of  the  sign  + ; thus,  the 
composition  of  sulphuric  acid  may  be  written  SO^,  or 
<S02+  Oy  the  latter  formula  implying  that  one  of  the  atoms 
of  oxygen  is  held  by  a feebler  affinity  than  the  other  two. 

When  a large  figure,  or  coefficient  is  placed  on  the  same 
line  as  the  symbol,  and  to  the  left  of  it,  it  multiplies  that  sym- 
bol as  far  as  the  first  comma  or  + sign  ; or,  if  the  formula  be 
placed  in  a parenthesis,  it  multiplies  every  letter  under  the 
parenthesis;  thus,  2SO^,  KO,  HO,  or  2SO^-\- KO-\- HO 
mean  two  atoms  of  sulphuric  acid  united  with  one  of  pot- 
ash and  one  of  water,  forming  the  bisulphate  of  potash  ; 
but  2(SO^,  KO,  HO.)  would  represent  two  atoms  of  a salt 
composed  of  one  of  sulphuric  acid,  one  of  potash,  and  one  of 
water,  the  figure  here  multiplying  all  under  the  parenthesis. 

The  advantages  which  arise  from  the  use  of  these  simple 
rules  are  very  great ; we  can,  even  with  the  most  complex 
bodies,  not  only  express  their  composition,  but  also  the  mole- 
cular arrangement,  or  grouping  of  their  atoms  ; we  can  fol- 
low them  through  the  most  intricate  changes,  and  without 
difficulty  trace  out  their  metamorphoses.  For  example, 
analysis  shows  that  alcohol  is  composed  of 

but  many  facts  in  its  history  lead  us  to  know  that  its  mole- 
cular constitution  is 

{C,H,)0  + H0; 

that  is  to  say,  it  contains  a compound  radical  C^H^,  to 
which  the  name  of  ethyl  has  been  given,  and  this  fact  be- 
ing understood,  we  see  at  once  that  upon  the  principles  of 
the  nomenclature  the  true  name  for  alcohol  is  the  hydrated 
oxide  of  ethyl ; moreover,  alcohol  is  derived  by  processes 
of  fermentation  from  sugar.  The  constitution  of  dry  grape 
sugar  is 

^12’  “^12’  ^12- 

How  is  the  comma  employed  ? What  is  the  use  of  the  sign  plus  ? How 
far  does  a coefficient  multiply  ? What  are  the  advantages  arising  from  the 
symbols  ? Give  an  example  in  the  case  of  alcohol. 


160 


LAWS  OF  COMBINATION. 


This  complex  atom,  under  the  influence  of  active  yeast,  is 
split  into 

2{C,H,0,) 4(C02), 

that  is  to  say,  into  two  atoms  of  alcohol  and  four  of  car- 
bonic acid  gas  ; and,  accordingly,  we  find,  during  ferment- 
ation, that  the  sugar  disappears,  alcohol  forming  in  the  liq- 
uid, and  carbonic  acid  gas  escapes. 

The  student  should  accustom  himself  to  the  translation 
of  the  nomenclature  into  symbols,  and  symbols  into  the 
nomenclature,  in  cases  where  it  is  possible,  for  it  is  abso- 
lutely essential  that  he  should  be  perfectly  familiar  with  the 
process. 


LECTURE  XXXVI. 

The  Laws  of  Combination. — Law  of  Fixed  Proportions. 
— Numerical  Law. — Multiple  Law. — Modes  of  ex^ 
pressing  Composition. — Proportions^  Equivalents^  and 
Atomic  Weights. — Relation  between  Combining  Yoh 
umes  and  Atomic  Weights.— Table  of  Specific  Gravi- 
ties and  Atomic  Weights. 

It  has  been  shown,  in  the  first  and  second  lectures,  that 
material  substances  possess  an  atomic  constitution,  and  all 
the  phenomena  of  chemistry  bear  out  this  conclusion.  It 
follows,  therefore,  when  substances  combine  with  each  other 
and  give  rise  to  new  products,  the  union  takes  place  by  the 
atoms  of  the  one  associating  themselves  with  the  atoms  of 
the  other,  and  as  these  atoms  possess  weight  and  other  prop- 
erties which  are  specific,  there  are  certain  circumstances, 
easily  foreseen,  which  must  attend  such  combinations. 

1st.  The  constitution  of  a compound  body  must  always 
be  fixed  and  invariable.  This  arises  from  the  fact  of  the 
unchangeability  of  the  properties  of  atoms  ; one  atom  of  wa- 
ter will  always  be  composed  of  one  atom  of  oxygen  and  one 
of  hydrogen ; one  atom  of  carbonate  of  lime  will  always 
consist  of  one  atom  of  carbonic  acid  and  one  of  lime.  Or, 
more  generally,  if  a good  analysis  of  water  has  shown  that 
nine  grains  of  that  substance  contain  eight  grains  of  oxygen 


In  -what  manner  does  the  combination  of  bodies  take  place  ? What  is 
meant  by  the  law  of  fixed  proportions  ? 


NUMERICAL  AND  MULTIPLE  LAWS. 


161 


and  one  of  hydrogen,  every  subsequent  analysis  will  corre- 
spond therewith. 

2d.  The  proportions  in  which  bodies  are  disposed  to  unite 
with  each  other  can  always  be  represented  by  certain  num- 
bers ; these  numbers  being,  in  fact,  the  relative  weights 
of  their  atoms.  Thus  water  is  composed  of  an  atom  of 
oxygen  and  one  of  hydrogen,  and  inasmuch  as  the  oxygen 
atom  is  eight  times  heavier  than  that  of  hydrogen,  it  neces- 
sarily follows  that  in  every  nine  parts  of  water  we  shall 
have  eight  of  oxygen  and  one  of  hydrogen.  These  numbers 
are  therefore  spoken  of  as  the  combining  proportions  or 
equivalents  of  the  substances  to  which  they  are  attached. 
If,  farther,  we  examine,  when  oxygen  and  sulphur  unite, 
what  are  the  relative  quantities,  we  shall  find  that  eight 
parts  of  oxygen  combine  with  sixteen  of  sulphur,  forming 
hyposulphurous  acid.  And  if  sulphur  and  hydrogen  unite, 
it  will  be  found  that  sixteen  of  sulphur  combine  with  one 
of  hydrogen.  In  this  manner,  by  examining  the  various 
elementary  bodies,  we  find  that  certain  numbers  are  ex- 
pressive of  the  proportions  in  which  they  are  disposed  to 
unite,  and  these  numbers  represent  the  relative  weight  of 
their  atoms  ; thus,  if  1 be  taken  as  the  atomic  weight  of  hy- 
drogen, that  of  oxygen  is  8,  that  of  sulphur  16,  &c. ; the 
atomic  weights  of  the  elementary  bodies  have  been  given 
in  Lecture  XXXIY. 

3d.  If  two  substances  unite  with  each  other  in  more  pro- 
portions than  one,  those  proportions  bear  a very  simple  arith- 
metical relation  to  one  another ; thus,  14  grains  of  nitro- 
gen will  successfully  unite  with  8,  16,  24,  32,  40  grains  of 
oxygen,  forming  successively  the  protoxide  of  nitrogen,  the 
deutoxide,  hyponitrous  acid,  nitrous  acid,  and  nitric  acid. 
And  when  the  numbers  expressing  the  amount  of  oxygen 
are  examined,  it  is  seen  that  they  are  in  the  second  twice, 
in  the  third  thrice,  in  the  fourth  four  times,  and  in  the  fifth 
five  times  the  amount  of  the  first ; they  are,  therefore,  sim- 
ple multiples  of  it.  The  reason  of  this  is  plain  when  we 
write  the  constitution  of  these  bodies  in  symbols ; they  are 
successively, 

NO  . . NO^ . . NO^ . . NO^  . . NO, ; 


What  by  the  numerical  law  ? Give  an  example  in  each  case.  What  do 
the  numbers  represent  ? Give  examples  of  these  numbers.  What  is  meant 
by  the  multiple  law  ? Give  an  example  of  it  in  the  case  of  the  compounds 
of  nitrogen  and  oxygen. 


162 


ATOMIC  WEIGHTS  OR  EOUIVALENTS. 


and  if  one  atom  of  oxygen  weighs  8,  two  must  weigh  16, 
three  24,  four  32,  &c. ; the  multiple  law,  therefore,  is  a 
necessary  consequence  of  the  combination  of  atoms. 

Observation  has  shown  that  there  are  two  series  accord- 
ing to  which  bodies  may  unite  with  each  other. 

(1.)  1 atom  of  A may  unite  with  1,  2,  .3,  4,  5,  &c.,  atoms  of  B. 

(2.)  1 atom  of  A may  unite  with  1,  l|,  2,  2|-,  3,  &c.,  atoms  of  B. 

But  as  an  atom  is  indivisible,  there  can  be  no  such  thing 
as  a half  atom  ; consequently  the  second  series  becomes, 

(3.)  2 atoms  of  A may  unite  with  1,  2,  3,  4,  5,  &c.,  atoms  of  B. 

The  three  foregoing  laws  are  known  under  the  name  of 
the  laws  of  combination  ; they  are  the  law  of  definite  pro- 
portions, the  law  of  numbers,  and  the  multiple  law. 

There  are  three  ways  in  which  the  composition  of  a sub- 
stance may  frequently  be  expressed;  1,  by  atom;  2,  by 
weight ; 3,  by  volume.  Thus,  the  constitution  of  water,  by 
atom,  is  one  of  oxygen  to  one  of  hydrogen  ; by  weight,  it  is 
one  of  hydrogen  to  eight  of  oxygen  ; and  by  volume,  two 
of  hydrogen  to  one  of  oxygen.  These  different  modes  of 
expression  involve  nothing  contradictory  ; they  are  all  recon- 
ciled by  the  statement  that  the  atom  of  oxygen  is  eight 
times  as  heavy  as  that  of  hydrogen,  but  only  half  the  size. 

By  some  authors  the  terms  combining  proportion  and 
equivalent  are  used ; they  have  the  same  signification  as 
atomic  weight.  And  as  we  know  nothing  of  the  absolute 
weight  of  atoms,  but  only  their  relative  proportions  to  each 
other,  we  may  select  any  substance  with  which  to  compare 
all  the  rest,  and  make  it  our  unit  or  term  of  comparison. 
In  this  book  hydrogen  is  employed  for  this  purpose,  and  its 
atomic  weight  is  marked  1 ; on  the  Continent  of  Europe 
oxygen  is  selected,  and  marked  100.  It  is  obvious  that  this 
does  not  afiect  the  relationship  of  the  numbers,  for  it  is  the 
same  thing  whether  we  state  the  atomic  weights  of  hydro- 
gen and  oxygen  as  1 to  8,  or  as  12J  to  100. 

Combinations  may  take  place  in  two  difierent  ways  : 1st, 
in  definite  proportions  ; 2d,  in  indefinite  proportions.  It  is 
to  the  former  that  all  the  foregoing  observations  and  laws 

What  are  the  two  series  in  which  bodies  may  unite  ? In  what  ways  may 
the  composition  of  a body  be  frequently  expressed  ? How  is  the  apparent 
contradiction  of  these  statements  reconciled?  What  do  proportion  and 
equivalent  signify  ? What  is  the  substance  with  w'hich  all  others  are  com- 
pared for  their  atomic  weights  in  this  book  ? What  other  standards  might 
be  employed?  What  are  the  two  modes  of  combination  ? 


SPECIFIC  GRAVITIES  AND  ATOMIC  WEIGHTS.  163 

apply.  One  grain  of  hydrogen  will  not  unite  with  nine  or 
seven  grains  of  oxygen,  but  only  with  eight.  But  one  drop 
of  spirits  of  wine  may  combine  with  one  of  water,  or  with 
a pint,  or  a quart,  or  ten  gallons.  This  is  what  is  under- 
stood by  union  in  indefinite  proportions.  ' 

When  two  gaseous  bodies  unite,  their  combining  propor- 
tions bear  a simple  relation  to  each  other ; one  volume  of 
hydrogen  unites  with  one  of  chlorine,  and  produces  two  vol- 
umes of  hydrochloric  acid.  And  in  the  case  of  the  five  com- 
pounds of  nitrogen  just  referred  to,  two  volumes  of  that  gas 
combine  successfully  with  1,  2,  3,  4,  5 of  oxygen. 

A relation,  therefore,  exists  between  the  combining  vol- 
ume and  the  atomic  weight  of  gaseous  bodies.  If  the  weight 
of  a given  volume  of  oxygen  be  called  100*0,  that  of  an  equal 
volume  of  hydrogen  will  be  6*25,  these  numbers  represent- 
ing, of  course,  the  specific  gravity  of  the  two  gases.  The 
proportion  in  which  they  unite  is  one  volume  of  oxygen  to 
two  of  hydrogen  to  form  water  ; the  relative  weights  of 
these  quantities,  therefore,  would  be  100  0 to  6*25  X 2,  that 
is,  100*0  to  12*50  ; but  these  numbers  are  the  atomic  weights 
of  the  bodies  respectively.  From  such  considerations,  it 
was  at  one  time  supposed  that,  in  the  case  of  all  gases,  the 
specific  gravities  would  correspond  to  the  atomic  weights. 
Experience  has,  however,  shown  that  this  is  not  the  case, 
as  is  seen  in  the  following  table  : 


Gas,  or  Vapor. 

Specific  Gravities. 

Chemical  Equivalents. 

Air  = 1. 

Hydropen  = 1. 

By  Volume. 

By  Weight. 

Hydrogen 

00690 

1-00 

100- 

1-00 

Nitrogen 

0-9727 

14*12 

100* 

14*15 

Carbon  (hypothetical)  . . . 

0-4213 

. 6-12 

100* 

6-12 

Chlorine 

2'4700 

35-84 

100- 

35-42 

Iodine 

8-7011 

126-30 

100* 

126-30 

Bromine 

5-3930 

78-40 

100- 

78-40 

Mercury 

6-9690 

101-00 

200* 

202-00 

Oxygen  

1-1025 

16  00 

50* 

8-00 

Phosphorus 

4*3273 

62-8 

25* 

15-70 

Arsenic 

10-3620 

150*8 

25- 

37-7 

Sulphur 

6-6480 

96-48 

16-66 

16-10 

From  this  it  is  seen,  that  if  the  combining  volume  of  hy- 
drogen, nitrogen,  or  chlorine  be  taken  as  unity,  that  of  oxy- 
gen is  one  half,  of  vapor  of  phosphorus  one  fourth,  and  of 
vapor  of  sulphur  one  sixth. 


What  relation  is  observed  when  gases  combine  by  volume  ? What  is  the 
relation  between  specific  gravities  and  atomic  weights  ? 


164  CALCULATION  OF  SPECIFIC  GRAVITIES. 


LECTURE  XXXVII. 

Constitution  of  Bodies. — Calculation  of  Specific  Grav- 
ities.— Crystallization. — Systems  of  Crystals. — Dimor- 
phism. — Isomorphism.  — Isomorphous  Groups. — Iso- 
merism.— Metameric  and  Polymeric  Bodies.  — Allo- 
tropic  States  of  Bodies. 

On  the  principles  which  have  just  been  developed,  we 
can  often  calculate  the  specific  gravity  of  a compound  gas 
with  more  accuracy  than  it  can  be  determined  experiment- 
ally. Thus,  hydrochloric  acid,  which  consists  of  equal  vol- 
umes of  chlorine  and  hydrogen  united,  without  condensation, 
must  have  a specific  gravity  of  1*2695,  because  the  specific 
gravity  of  hydrogen  being  0*0690,  and  that  of  chlorine 
2*4700,  the  sum  of  which,  2*5390,  is  the  weight  of  two 
volumes  of  hydrochloric  acid,  and,  therefore,  if  we  divide  by 
2,  the  quotient,  1*2695,  is  equal  to  the  weight  of  one  vol- 
ume ; or,  in  other  words,  the  specific  gravity  of  the  com- 
pound gas. 

Sometimes,  also,  we  can  determine  the  specific  gravity 
of  a vapor  by  calculation  when  it  is  impossible  to  do  so  ex- 
perimentally. Assuming  that  one  volume  of  carbonic  acid 
gas  contains  one  volume  of  oxygen  and  one  of  carbon  vapor, 
we  have. 


Specific  gravity  of  carbonic  acid  . . . 1'5238 

“ “ oxygen 1T025 

“ “ carbon  vapor  . . , *4213 


The  hypothetical  specific  gravity  of  the  vapor  of  carbon  is 
therefore  ’4213. 

The  rule  for  the  calculation  of  specific  gravities,  on  the 
foregoing  principles,  is,  “ Multiply  the  specific  gravities  of 
the  simple  gases  or  vapors  respectively  by  the  volumes  in 
which  they  combine,  add  those  products  together,  and  di- 
vide the  sum  by  the  number  of  volumes  of  the  compound 
gas  produced.” 

How  may  the  specific  gravity  of  a compound  gas  be  determined  ? How 
is  the  hypothetical  specific  gravity  of  the  vapor  of  carbon  determined? 
What  is  the  rule  for  the  calculation  of  the  specific  gravities  of  compound 
gases  from  those  of  their  constituents  ? 


SYSTEMS  OF  CRYSTALLIZATION. 


165 


It  frequently  happens  that  substances  assuming  the  solid 
form,  from  the  liquid  or  vaporous  states,  take  on  a geomet- 
rical figure,  being  terminated  by  sharp  edges  and  solid  an- 
gles ; under  such  circumstances,  they  are  said  to  crystallize. 
Thus,  common  salt  will  crystallize  in  cubes,  and  nitrate  of 
potash  in  six-sided  prisms. 

The  various  geometrical  forms  which  crystals  can  thus 
assume  may  be  divided  into  six  classes,  or  systems  : 

(1.)  The  Regular  system. 

(2.)  The  Rhombohedral  system. 

(3.)  The  Square  Prismatic  system. 

(4.)  The  Right  Prismatic  system. 

(5.)  The  Oblique  Prismatic  system. 

(6.)  The  Doubly  Oblique  Prismatic  system. 

This  division  is  founded  on  the  relations  of  certain  lines, 
or  axes,  which  may  be  supposed  to  be  drawn  through  the 
centre  of  the  crystal  round  which  its  parts  are  symmetri- 
cally arranged. 

THE  REGULAR  SYSTEM. 

This  has  three  equal  axes  at  right  angles  to  each  other. 

Fig.  142. 


The  letters  a a show  the  direction  of  the  axes.  The 
figure  {Fig-  142)  represents,  1.  The  cube  ; 2.  Regular  oc- 
tahedron ; and,  3.  Rhombic  dodecahedron. 

THE  SQUARE  PRISMATIC  SYSTEM. 

This  has  three  axes,  two  of  which  are  equal,  and  the 
third  of  a different  length. 

.c;  a a is  the  principal  axis  ; b b the  secondary  one.  In  the 
figure  {Fig.  143),  1 is  a right  square  prism,  with  the  axes 
on  the  centre  of  the  sides,  b b ; 2 is  a right  square  prism, 
with  the  axes  in  the  edges  ; 3 and  4 corresponding  right 
square  octahedrons. 

What  are  the  six  systems  of  crystallization?  Upon  what  fact  is  this 
division  founded  ? In  the  regular  system,  what  is  the  relation  of  the  axes  ? 
In  the  square  prismatic  system,  what  is  their  relation? 


16G 


SYSTEMS  OF  CRYSTALLIZATION. 


THE  RIGHT  PRISMATIC  SYSTEM 

has  three  axes,  a a,  h b,  c c,  of  unequal  lengths,  at  right 
angles  to  each  other. 

Fig.  144. 


In  the  figure  {Fig,  144),  1 is  a right  7'ectangular  'prism; 
2.  Right  rhombic  'prism  ; 3.  Right  rectangular  based  oc- 
tahedron; 4.  Right  rhombic  based  octahedron. 


THE  OBLIQUE  PRISMATIC  SYSTEM 

has  three  axes,  which  may  be  unequal ; two  are  placed  at 
right  angles  to  each  other,  and  the  third  is  oblique  to  one 
and  perpendicular  to  the  other. 

145. 


What  is  it  in  the  right  prismatiC?  In  the  oblique  and  double  oblique 
prismatic  systems,  what  is  it  ? 


SYSTEMS  OF  CRYSTALLIZATION. 


167 


In  the  figure  {Fig.  145),  1 is  an  oblique  rectangular 
prism;  2.  Oblique  rhombic  prism;  3.  Oblique  rectan- 
gular based  octahedron ; 4.  Oblique  rhombic  based  octa- 
hedron. 

THE  DOUBLY  OBLIQUE  PRISMATIC  SYSTEM 

has  three  axes,  which  may  be  all  unequal  and  all  oblique. 
Fig.  146. 


In  the  figure  {Fig,  146),  1 and  2 are  doubly  oblicpie 
prisms  ; and  3 and  4 doubly  oblique  octahedrons. 

THE  BHOMBOHEDRAL  SYSTEM 

has  four  axes,  three  of  which  are  equal  in  the  same  plane, 
and  inclined  at  angles  of  60^  ; the  fourth,  which  is  the 
principal  axis,  is  perpendicular  to  all. 


Fig.  147. 


In  the  figure  {Fig.  147),  1 is  the  regular  six-sided 
prism;  2,  the  dodecahedron;  3.  Fhombohedron ; 4,  an- 
other dodecahedron. 

It  often  happens,  owing  to  a change  in  the  deposit  of 
new  matter  on  a crystal  while  forming,  that  other  figures 
than  the  proper  one  are  produced  ; thus,  the  cube  may  pass 
into  the  octahedron,  as  shown  in  Fig.  148. 

How  many  axes  are  in  the  rhombohedral  system,  and  what  is  their  rela- 
tion ? In  what  manner  may  crystals  of  one  form  pass  into  those  of  another, 
as  the  cube  into  the  octahedron  ? 


168 


GONIOMETERS. 


Fig.  148. 


The  effect  may,  perhaps,  be  better  conceived  by  imagining 
the  solid  angle  of  the  cube  1 to  be  cut  off  by  planes  equally 
inclined  to  the  constituent  faces.  2 represents  an  increased 
removal  of  the  same  kind  ; 3 one  still  farther  advanced. 

Sometimes  it  happens  that  each  alternate  plane  of  a crys- 
tal grows  at  the  expense  of  the  adjacent  one,  giving  rise  to 
hemihedraly  or  half-sided  crystals,  as  is  shown  in  Fig.  149, 
which  represents  the  tetrahedron,  arising  in  this  manner 
from  the  octahedron  by  the  growth  of  each  alternate  face. 
1 . The  octahedron  partially  modified ; 2.  The  change  far- 
ther advanced  ; 3.  The  tetrahedron  completed. 


Fig.  149. 


The  angles  of  crystals  are  measured  by  goniometers,  of 
150.  which  there  are  several 

kinds ; as  the  common  goni- 
ometer, and  Wollaston’s  re- 
flecting goniometer.  This 
instrument  is  represented  in 
Fig.  150.  The  ciystal  to 
be  measured,  /,  is  fixed 
upon  a movable  support,  d, 
which  is  in  connection  with 
the  button-headed  axis  of 
the  goniometer,  o,  which 
passes  through  a larger  axis 
in  the  upright,  h.  is  a di- 
vided circle,  and  e its  ver- 
nier, which  is  fixed  immovably  on  the  upright,  h. 

The  edge  of  the  crystal,  which  is  formed  by  the  two  faces 


What  are  hemihedral  crystals,  and  how  are  they  produced  ? Describe 
the  use  of  the  reflecting  goniometer. 


DIMORPHISM. 


169. 


whose  inclination  is  to  be  measured,  is  to  be  set  parallel  to 
the  axis  of  the  instrument ; and  having,  by  means  of  the 
button,  0,  turned  the  crystal  until  some  definite  object,  such 
as  the  bar  of  a window,  is  seen  distinctly  reflected  from  it, 
the  larger  milled  head  is  turned,  and  with  it  the  divided 
circle  and  crystal,  until  the  same  object  is  again  seen  by 
reflection  from  the  second  face.  The  angle  through  which 
the  great  circle  has  moved,  subtracted  from  180°,  gives 
the  angle  included  between  the  two  crystalline  faces,  or 
their  inclination  to  eaph  other. 

As  a general  rule,  the  same  substance,  crystallizing  un- 
der the  same  circumstances,  will  produce  crystals  belonging 
to  the  same  system.  Cases,  however,  are  known  in  which 
the  same  substance  belongs  to  different  systems.  Thus, 
sulphur  will  crystallize  in  rhombic  prisms,  and  also  rhombic 
octahedrons.  By  dimorphous  bodies  we  therefore  mean 
substances  which  will  aflbrd  crystals  belonging  to  two  dif- 
ferent systems. 

Dimorphism  is  frequently  connected  with  the  temperature 
at  which  the  crystals  were  produced.  Thus,  carbonate  of 
lime,  at  ordinary  temperatures,  yields  rhombohedrons,  but 
at  the  boiling  point  of  water  right'  rhombic  prisms ; and 
with  this  difference  of  form  a diflerence  of  chemical  quali- 
ties may  occur ; the  bisulphuret  of  iron,  for  example,  crys- 
tallizes in  cubes,  which  remain  unacted  upon  by  water  or 
air  ; but  in  its  right  rhombic  form  it  undergoes  rapid  oxyda- 
tion  in  moist  air,  producing  sulphate  of  iron.  Commonly 
one  of  the  forms  of  a dimorphous  body  is  less  stable  than 
the  other,  and  if  the  transition  takes  place  abruptly,  it  is 
sometimes  attended  by  a flash  of  light. 

It  was  discovered  by  Mitscherlich,  that  when  different 
compound  bodies  assume  the  same  form,  we  are  often 
able  to  trace  a remarkable  analogy  in  their  chemical  com- 
position. Thus,  the  chloride  of  sodium,  the  iodide  of  po- 
tassium, the  fluoride  of  calcium,  &c.,  crystallize  in  the 
first  system.  These  substances  are  all  constituted  upon 
a common  type,  in  which  we  have  one  atom  of  a metal 
united  to  one  atom  of  an  electro-negative  radical ; or,  tak- 
ing M as  the  general  symbol  for  the  metals,  and  R for  the 


What  is  meant  by  dimorphous  bodies  ? What  effect  has  temperature  on 
the  formation  of  crystals  ? Is  dimorphism  connected  with  peculiarities  in 
the  chemical  qualities  of  bodies  ? What  relation  is  there  in  the  form  and 
composition  of  iodide  of  potassium  and  chloride  of  sodium  ? 

H 


170 


ISOMORPHISM. 


electro-negative  radicals,  the  class  is  constituted  upon  the 
type 

M,  jK, 

and  therefore  includes  such  bodies  as 

KCl . . NaCl . . KBr.,  KF. . CaF.  AmCl . . . &c. 


Such  substances  are  called  isomorphous  bodies,  and  the  des 
ignations,  isomorphous  elements,  isomorphous  groups,  are 
used,  being  derived  from  Loog,  equal,  fiopcbrj,  form. 

Let  us  take  a second  more  complicated  case.  The 
formula  for  common  alum,  the  sulphate  of  alumina  and 
potash,  is. 


Ammonia  alum  is 
Chrome  alum  is 
Iron  alum  is 


KO,  SO^ 
AmO,  SO3 
KO,  SO3 
KO,  SO3 


• Al^  O3,  3SO3 
■Al^  03,  3503 


-24HO. 

-24HO. 

-24HO. 

-24HO. 


And  in  the  same  way  an  extensive  family  of  alums  may  be 
formed  by  the  substitution  of  a limited  number  of  various 
other  bodies  comprised  in  the  general  formula, 
mO,  SOs  + Mg  O3,  3SO^  + 24ATO, 
in  which  m represents  any  metal  belonging  to  the  potassium 
group,  and  M any  one  belonging  to  the  aluminum  group. 

All  these  alums  crystallize  with  the  same  form,  and  such 
illustrations  afford  us  reason  to  believe  that  that  similarity 
of  form  is  due,  in  a great  measure,  to  the  grouping  or  ar- 
rangement of  the  constituent  atoms  ; that  in  a compound 
molecule  the  substances  lohich  can  replace  one  another 
without  giving  rise  to  a change  of  external  form  must 
have  certain  relationships  to  each  other.  We  call  them^ 
therefore,  isomorphous.  The  following  ten  groups  have 
been  established  : 


1. 

Silver Ag 

Gold Au 

2. 

Arsenious  Acid  (in  its 

unusual  form)  . . . A.S3  O3 

Sesquioxide  of  Antimo- 
ny   56a  O3 

3. 

Alumina Al^  O3 

Sesquioxide  of  Iron  . Fe^  O3 


Sesquioxide  of  Chro- 
mium   Cra  O3 

Sesquioxide  of  Manga- 
nese   Mn^  O3 

4. 

Phosphoric  Acid  . . P3O3 

Arsenic  Acid . . . . As^  O5 

5. 

Sulphuric  Acid  . . . S O3 

Selenic  Acid  . ...  Se  O3 

Chromic  Acid  . . . Cr  O3 

Manganic  Acid  . . . Mn  Og 


Why  are  they  called  isomorphous  bodies  ? Give  an  example  ofisomorph 
ism  in  the  case  of  the  alums.  What  general  conclusion  may  be  drawn 
from  these  facts  ? How  many  isomorphous  groups  have  been  determined . 
Enumerate  the  members  belonging  to  each. 


ISOMERISM. METAMERIC  AND  POLYMERIC  BODIES.  171 


6. 

Lime  (in  arragonite)  . 
Oxide  of  Lead  . . . 

Ca  0 

Hypermanganic  Acid  . 

O7 

Pb,0 

Hyperchloric  Acid  . . 

Cl  O7 

10. 

7. 

Lime  (in  Iceland  spar) 

Ca  0 

Salts  of  Potash  . . . 

K.O 

Magnesia 

MgO 

Salts  of  Oxide  of  Am- 

Protoxide of  Iron  . . 

Fe  0 

monium  

Am  0 

(( 

Manganese 

Mn  0 

8. 

u 

Zinc  . . 

Zn  0 

Oxide  of  Silver  . . . 

AgO 

({ 

Cobalt  . . 

Co  0 

Oxide  of  Sodium  . . 

Na  0 

u 

Nickel  . . 

Ni  0 

9. 

u 

Copper . . 

Cu  0 

Baryta 

Ba  0 

(< 

Lead  ( in 

Strontia 

Sr  0 

plumbo  calcite)  . . 

Pb.O 

From  the  external 

forms  of  bodies  we 

may  next  turn  to 

their  internal  constitution,  calling  to  mind  what  has  been 
already  observed  in  Lecture  XXXV.,  that  identity  of  com- 
position by  no  means  implies  identity  of  character.  Two 
substances  may  be  composed  of  the  same  elements,  united 
in  the  same  proportions,  and  yet  be  totally  unlike  ; and  it 
is  obvious  that  this  may  be  due  to  two  different  causes  : 
1st.  Difference  of  grouping ; 2d.  Difference  in  the  absolute 
number  of  atoms. 

Difference  of  grouping  I have  already  explained  in  the 
lecture  just  quoted  ; and  with  respect  to  difference  in  the 
absolute  number  of  atoms,  the  effect  is  obvious  from  an  ex- 
ample. Thus,  we  have  as  the  constitution  of 

Aldehyde 

Acetic  ether CqHqO^. 

And  these  bodies,  if  analyzed,  would,  of  course,  yield  pre- 
cisely the  same  proportions  in  100  parts,  the  true  difference 
being,  that  the  atom  of  acetic  ether  contains  twice  as  many 
constituent  atoms  as  that  of  aldehyde,  and  is,  therefore,  ex 
actly  twice  as  heavy,  though  equal  weights  of  the  two  wib 
yield  equal  quantities  of  their  constituents. 

To  these  peculiarities  the  term  isomerism  is  applied,  and 
by  isomeric  bodies  We  mean  bodies  composed  of  the  same 
elements  in  the  same  proportion,  but  differing  in  properties. 
When  isomerism  arises  from  difference  in  grouping,  the 
bodies  are  said  to  be  metameric  ; and  when  it  arises  from 
difference  in  the  absolute  number  of  atoms,  they  are  called 
polymeric. 

Attention  has  recently  been  drawn  to  a third  cause,  which 

What  two  causes  may  give  to  bodies  of  the  same  composition  different 
characters?  Give  an  example  of  the  effect  of  difference  of  the  absolute 
number  of  atoms.  What  is  meant  by  isomerism  ? What  are  metameric 
bodies  ? What  are  polymeric  bodies  ? 


172 


ALLOTROPISM, 


gives  rise  to  the  phenomena  of  isomerism  : it  is  the  allo- 
tropic  condition  of  elementary  bodies.  Carbon,  for  example, 

exists  under  a number  of  different  forms ; we  find  it  as  char- 
coal, plumbago,  and  diamond.  They  differ  in  specific  grav- 
ity, in  specific  heat,  and  in  their  conducting  power  as  re- 
spects caloric  and  electricity.  In  their  relations  to  light, 
the  one  perfectly  absorbs  it,  the  second  reflects  it  like  a 
metal,  the  third  transmits  it  like  glass.  In  their  relation  to 
oxygen  they  also  differ  surprisingly ; there  are  varieties  of 
charcoal  that  spontaneously  take  fire  in  the  air,  but  the  dia- 
mond can  only  be  burned  in  pure  oxygen  gas.  The  second 
and  third  varieties  do  not  belong  to  the  same  crystalline 
form. 

It  is  now  known  that  a great  many  elementary  substan- 
ces are  affected  in  this  manner.  I have  shown  that  this  is 
the  case  with  chlorine  gas,  which  changes  under  the  influ- 
ence of  the  indigo  rays  (Fhil.  Mag.^  July,  1844).  In  the 
same  manner,  it  has  been  long  known  that  iron  exists  in 
two  states  : 1st.  In  its  ordinary  oxydizable  state  ; 2d.  In  a 
condition  in  which  it  simulates  the  properties  of  platinum 
or  gold. 

There  can  be  no  doubt  that  these  peculiarities  are  car- 
ried by  these  bodies  when  they  unite  to  form  compounds ; 
thus,  for  example,  if  carbon  and  hydrogen  unite,  it  is  pos- 
sible we  may  have  three  different  compounds  ; one  con- 
taining charcoal  carbon,  a second  plumbago  carbon,  a third 
diamond  carbon  ; or,  if  we  designate  these  respectively  as 
Ca,  Cj3,  Cy,  we  may  have 

CaK. . . cm- . . CyH; 

and  perhaps,  as  M.  Millon  has  suggested,  carbureted  hy 
drogen  gas  and  otto  of  roses,  which  have  the  same  consti 
tution,  differ,  in  the  one  containing  charcoal  and  the  other 
diamond. 

These  peculiarities  are  known  under  the  name  of  allo- 
tropic  states,  and  the  phenomenon  itself  under  the  designa- 
tion of  allotropism. 

What  is  meant  by  the  allotrcmic  condition  of  bodies  ? What  allotropic 
states  does  carbon  present  ? How  may  an  allotropic  change  be  impressed 
on  chlorine  ? What  are  the  allotropic  states  of  iron  ? Are  these  peculiar- 
ities continued  in  the  compounds  ? 


CHEMICAL  AFFINITY. 


173 


LECTURE  XXXVIII. 

Chemical  Affinity. — Phenomena  accompanying  Chemi‘ 
cal  Affinity, — Disturbance  of  Temperature. — Produc- 
tion of  Light. — Evolution  of  Electricity. — Change  of 
Color. — Change  of  Form. — Change  of  Chemical  Prop- 
erties.— Change  of  Volume  and  Density. — Tables  of 
Geoffroy. — Measure  of  Affinity. — Disturbing  Causes. 

By  chemical  affinity  we  mean  the  attraction  of  atoms  of 
a dissimilar  nature  for  each  other,  an  attraction  which  is 
exhibited  upon  the  apparent  contact  of  bodies. 

There  are  certain  striking  phenomena  which  very  fre- 
quently accompany  chemical  action.  They  are  the  evolu- 
tion of  Light,  Heat,  and  Electricity ; and,  as  respects  the 
bodies  engaged,  they  may  exhibit  changes  of  color,  of  form, 
of  volume,  of  density,  or  of  their  chemical  properties,  35^ 

If,  in  a glass  vessel,  a {Fig.  151),  a mixture  of 
strong  sulphuric  acid  and  water  be  stirred  together 
by  means  of  a tube,  b,  containing  some  sulphuric 
ether,  so  much  heat  will  be  evolved  by  the  acid 
and  water  as  they  unite,  that  the  ether  will  be 
made  to  boil  rapidly. 

If,  upon  some  water  contained  in  a shallow  dish  {Fig. 
152),  a piece  of  potassium  be  thrown,  the  po-  150 

tassium  decomposes  the  water  with  the  evolu- 
tion of  a beautiful  lilac  flame. 

As  respects  the  evolution  of  electricity  dur- 
ing chemical  action,  the  Voltaic  battery,  and, 
indeed,  all  Voltaic  combinations,  are  examples. 

In  the  simple  circle  we  have  already,  in  Lecture  XXIX., 
traced  the  production  of  electricity  to  the  decomposition  of 
the  water. 

"We  have  observed  that  the  evolution  of  the  imponder- 
able agents  is  not  the  only  phenomenon  to  be  remarked 
during  the  play  of  chemical  affinity  ; the  ponderable  sub- 
stances themselves  undergo  changes. 

What  is  meant  by  chemical  affinity  ? What  phenomena  accompany  chem. 
ical  action  ? What  changes  are  exhibited  by  the  ponderable  bodies  them, 
selves  1 Give  examples  of  the  evolution  of  heat,  light,  and  electricity. 


174 


CHANGES  OP  COLOR  AND  FORM. 


If,  in  a glass  containing  litmus  water,  a drop  of  sulphur! 
acid  is  poured,  the  blue  color  of  the  litmus  is  at  once  chang- 
ed to  a red,  and  if  into  the  reddened  fluid  so  produced  a lit- 
tle ammonia  is  poured,  the  blue  color  is  restored.  This 
simple  experiment  is  of  considerable  interest,  for  the  red- 
dening of  litmus  is  commonly  received  as  one  of  the  attri- 
butes of  acid  bodies,  and  the  restoration  of  the  blue  color  oil. 
those  belonging  to  the  alkaline  type. 

On  adding  to  a solution  of  sulphate  of  copper  a small 
quantity  of  ammonia,  a pale  green  precipitate  is  thrown 
down ; a greater  quantity  of  ammonia  redissolves  this  pre- 
cipitate, and  gives  rise  to  a splendid  purple  solution. 

A similar  solution  of  sulphate  of  copper  gives  rise,  under 
the  action  of  a solution  of  ferrocyanide  of  potassium,  to  a 
deep  chocolate-colored  precipitate. 

A solution  of  the  nitrate  of  lead,  which  is  colorless,  acted 
on  by  a solution  of  iodide  of  potassium,  also  colorless,  gives 
rise  to  the  production  of  a beautiful  yellow  precipitate,  the 
iodide  of  lead. 

And,  lastly,  if  sulphuric  acid  be  placed  in  a solution  of  a 
soluble  salt  of  lead,  or  of  baryta,  a white  precipitate  at  once 
goes  down. 

These  are  all  instances  of  changes  of  color,  and  such 
changes  are  of  the  utmost  importance  in  practical  chem- 
istry, inasmuch  as  the  art  of  testing  depends,  for  the  most 
part,  upon  a knowledge  of  them. 

Changes  of  form  in  the  same  manner  are  exhibited  ; thus, 
when  gunpowder  explodes,  a large  proportion  of  the  ingre- 
dients, from  being  in  the  solid,  escapes  in  the  gaseous  state. 
If,  upon  fragments  of  chalk,  carbonate  of  lime,  we  pour  hy- 
drochloric acid,  a violent  effervescence  takes  place,  due  to 
the  escape  of  carbonic  acid,  which,  from  being  in  the  solid, 
assumes  the  gaseous  form. 

The  converse  of  this  is  sometimes  seen,  vapors 
passing  into  the  solid  state.  In  the  glass,  a {Fig. 
153),  place  some  strong  hydrochloric  acid,  and 
in  b some  strong  ammonia ; both  these  bodies 
yield  vapors  at  ordinary  temperatures  in  abund- 
ance, and  those  vapors  meeting  in  the  air  over 
the  glasses,  give  rise  to  a dense  fume  or  smoke, 
which,  if  examined,  proves  to  be  solid  sal  ammoniac. 

Give  examples  of  changes  of  color.  On  what  do  the  processes  of  testing 
(or  the  most  part  depend?  Give  an  example  of  the  production  of  a gas 
from  a solid,  and  a solid  from  gases. 


Fig.  153. 


CHANGES  OF  PROPERTIES. 


175 


Very  often  change  of  form  is  accompanied  by  jp/^.154. 
change  of  color  ; thus,  if  under  a large  bell  jar 
{Fig.  154)  there  is  placed  a wine-glass  contain- 
ing a few  copper  or  iron  nails  and  nitric  acid,  a 
gas  of  a deep  orange  color  makes  its  appearance, 
filling  the  whole  bell. 

Perhaps  no  better  instance  of  an  entire  change 
of  properties  could  be  cited  than  that  of  the  com- 
bustion of  phosphorus  in  atmospheric  air.  This  substance, 
phosphorus,  is  a body  of  a waxy  appearance,  possessing  so 
great  a degree  of  combustibility  that  it  requires  to  be  kept 
under  the  surface  of  water  to  prevent  the  action  of  the  air. 
If  a piece  of  it  be  set  on  fire  beneath  a clear 
and  dry  bell  jar,  as  shown  in  Fig.  155,  it 
unites  with  great  energy  with  the  oxygen 
of  the  included  air,  producing  white  flakes, 
which,  as  the  combustion  is  ceasing,  descend 
in  the  jar,  giving  a miniature  representation 
of  a fall  of  snow.  On  collecting  some  of 
this  phosphoric  snow,  its  properties  will  be 
found  to  be  in  striking  contrast  with  the 
phosphorus  which  produced  it ; for  instance,  far  from  being 
unacted  on  by  water,  it  has  such  an  intense  affinity  for  that 
substance,  that  it  hisses  like  a red-hot  iron  when  brought 
in  contact  with  it.  It  reddens  litmus  solution,  and  pos- 
sesses the  qualities  of  a powerful  acid.  Nor  is  the  change 
confined  to  the  phosphorus  ; if  we  examine  the  air  in  which 
it  was  burned,  we  find  it  has  lost  its  quality  of  supporting 
combustion. 

Changes  of  volume,  and,  consequently,  changes  of  dens- 
ity, constantly  attend  chemical  action  ; a pint  of  water  and 
a pint  of  sulphuric  acid,  mixed  together,  form  less  than  two 
pints  ; and  the  same  may  be  observed  of  alcohol  and  water. 

When  to  two  substances  already  in  union,  a third,  hav- 
ing a stronger  affinity  for  one  of  the  other  two,  is  presented, 
decomposition  ensues.  Thus,  if  to  the  carbonate  of  soda 
nitric  acid  be  presented,  the  soda  and  nitric  acid  combine, 
and  the  carbonic  acid  is  driven  off  in  the  form  of  a gas. 
And,  again,  if  upon  the  nitrate  of  soda  so  produced  sulphuric 
acid  is  poured,  the  nitric  acid  is  driven  off,  and  sulphate  of 

What  are  the  changes  which  phosphorus  undergoes  when  burned  in  the 
air  ? Give  an  example  of  change  of  volume  and  of  density.  Under  what 
circumstances  does  decomposition  take  place  ? 


Fig.  155. 


176 


MEASURE  OF  CHEMICAL  AFFINITY. 


soda  results.  It  was  at  one  time  thought  that,  by  examin- 
ing a number  of  such  cases,  we  might  discover  the  order 
of  affinity  of  bodies  for  one  another,  and  arrange  them  in 
tables  ; these  are  sometimes  called  the  Tables  of  Geoffrey. 
Thus,  the  table 

Soda. 

Sulphuric  acid. 

Nitric  “ 

Muriatic  “ 

Acetic  “ 

Carbonic 

presents  us  with  the  order  in  which  a number  of  acids 
stand  in  relation  to  soda,  the  most  powerful  being  the  first 
on  the  list,  and  the  salt  which  results  from  the  union  of 
any  one  of  those  acids'with  the  soda  can  be  decomposed 
by  the  use  of  any  other  acid  standing  higher  on  the  list. 

But  it  is  now  known  that  these  tables  are  far  from  rep- 
resenting the  order  of  affinities  ; a weaker  affinity  often 
overcomes  a stronger,  by  reason  of  the  intervention  of  dis- 
turbing extraneous  causes ; and  tables  so  constructed  lead, 
therefore,  to  contradictory  conclusions.  Some  very  simple 
considerations  may  illustrate  this.  Potassium  can  take  oxy- 
gen from  carbon  at  low  temperatures,  or,  in  other  words, 
decompose  carbonic  acid  gas,  but  it  by  no  means  follows 
that  the  affinity  of  potassium  for  oxygen  is  greater  than 
that  of  carbon,  and  accordingly  we  find  that  at  higher  tem- 
peratures carbon  can  take  oxygen  from  potassium.  Indeed, 
under  the  influence  of  heat,  light,  and  electricity,  we  find 
all  kinds  of  chemical  changes  going  on,  and  in  the  same 
manner  the  condition  of  form  exerts  a remarkable  influence 
in  these  respects,  so  that  cohesion  and  elasticity  may  be 
placed  among  the  predisposing  causes  producing  chemical 
results.  If  a number  of  bodies  exist  in  a solution  together, 
they  will  at  once  arrange  themselves  in  such  a way  under 
the  influence  of  cohesion  as  to  produce  insoluble  precipitates, 
if  that  be  possible  ; or,  under  the  influence  of  elasticity,  to 
determine  the  evolution  of  a gas  ; if  the  carbonate  of  soda 
is  decomposed  by  acetic  acid,  it  by  no  means  follows  that 
the  latter  has  the  stronger  affinity  for  soda,  the  decomposi- 

Wbat  are  the  tables  of  Geoffroy  ? How  may  it  be  shown  that  these  are 
not  the  tables  of  affinity  ? What  may  be  enumerated  among  these  disturb- 
ing causes?  What  is  the  influence  of  cohesion?  What  is  the  influence 
of  elasticity  ? Give  examples  of  the  action  of  these  disturbing  agents. 


TABLES  OP  GEOFPROY. 


177 


tion  being  probably  determined  by  the  fact  that  the  car- 
bonic acid  can  take  on  the  elastic  form  and  escape  away  as 
a gas.  The  sulphate  of  soda  may  be  decomposed  by  bary- 
ta, the  cause  of  the  decomposition  being  probably  due  to 
cohesion,  for  the  sulphate  of  baryta  which  results  is  a very 
insoluble  body.  We  have,  therefore,  no  true  measure  of 
affinity,  for  the  relation  of  bodies  in  this  respect  changes 
with  external  conditions,  and  the  tables  of  Geoffroy  are  only 
tables  of  the  order  of  decompositions,  but  not  of  the  order 
of  affinity. 


What  do  the  tables  of  Geoffroy,  in  reality,  express  ? 

H 2 


PART  III. 

INORGANIC  CHEMISTRY. 


LECTURE  XXXIX. 

Pneumatic  Chemistry. — Ancient  Opinions  on  the  Consti- 
tution of  the  Gases. — Doctrine  of  the  Unity  of  Air. 
Oxygen  Gas. — Modes  of  Preparation. — Properties. — Ori- 
gin of  its  Name. — Relations  to  Atmospheric  Air  and 
Combustion. — Burning  of  Metals. 

In  the  catalogue  of  the  elementary  bodies  of  the  ancients 
four  substances  were  included,  earth,  air,  fire,  and  water. 
The  progress  of  knowledge  has  shown  that  three  out  of  the 
four  are  compound  bodies. 

For  a length  of  time  it  was  supposed  that  the  variout 
exhalations  and  vapors  were  nothing  more  than  vitiated 
forms  of  atmospheric  air ; and  though  from  time  to  time 
first  one  and  then  another  of  the  gaseous  bodies  was  discov- 
ered, chemists  were  slow  to  admit  that  they  were  any  thing 
more  than  modifications  of  one  common  principle.  Thus, 
Roger  Bacon,  in  the  thirteenth  century,  discovered  one  of 
the  carburets  of  hydrogen,  and  Van  Helmont,  in  the  six- 
teenth, carbonic  acid.  The  invisibility  of  these  bodies,  their 
remarkable  chemical  relations  in  extinguishing  flame  and 
producing  death,  the  great  mechanical  force  to  which  they 
often  gave  rise  when  generated  in  pent-up  vessels,  their  oc- 
currence in  mines,  the  bottom  of  wells,  in  church-yards  and 
lonely  places,  suggested  to  a superstitious  mind  a supernat- 
ural origin,  and  Van  Helmont  gave  them  the  name  of  gas, 
corrupted  from  gahst  (or  geist),  which  signifies  a ghost  or 
spirit. 

But  it  is  to  the  researches  on  the  properties  of  fixed  air, 
which  Black  made  about  1750,  that  pneumatic  chemistry 
owes  its  origin.  These  were  soon  followed  by  the  discov- 
eries of  Priestley,  Scheele,  and  others.  That  of  oxygen  gas, 

What  opinions  were  formerly  held  respecting  the  different  gases  ? 
What  was  the  original  signification  of  the  term  gas  ? By  whom  was  the 
doctrine  of  the  plurality  of  airs  established  ? 


PREPARATION  OF  OXYGEN. 


179 


by  the  former  of  these  philosophers,  in  1784,  forever  destroy- 
ed the  ancient  notion  of  vitiated  airs ; for  this  gas  can  sup- 
port combustion  and  respiration  far  better  than  the  atmos- 
phere. It  may  be  said  with  justice  that  modern  chemistry 
dates  its  origin  from  the  discovery  of  oxygen  gas. 

OXYGEN.  O = 8013. 

Oxygen  gas  is  probably  the  most  abundant  of  the  ele- 
ments. It  constitutes  about  one  third  of  the  weight  of  the 
solid  mass  of  the  earth,  eight  ninths  of  that  of  the  waters 
of  the  sea,  and  one  fifth  the  volume  of  the  air. 

A simple  mode  of  preparing  oxygen  is  to  place  in  a re-^ 


tort,  a,  Fig,  156,  some  red  oxide  of  mercury,  connecting 
with  the  retort  a receiver,  b,  from  which  there  passes  a 
bent  tube,  c,  which  dips  beneath  the  water  of  a pneumatic 
trough,  g.  On  raising  the  temperature  of  the  oxide  by  the 
flame  of  a spirit  lamp,  it  is  resolved  into  metallic  mercury 
and  oxygen  gas  ; the  former  distills  into  the  receiver  and 
the  latter  collects  in  the  inverted  jar  of  the  trough. 

Another  process  is  to  place  the  peroxide  of  manganese 
{Mji.  Og)  in  an  iron  bottle,  from  which  a tube,  h,  Fig.  157, 
projects  ; this  tube  may  be  connected  with  another,  f,  by 
means  of  a cork  and  an  India-rubber  tube,  e.  The  bottle 
is  to  be  arranged  in  a small  furnace,  and  made  red  hot ; 
the  manganese  loses  one  fourth  of  its  oxygen,  which  may 
be  collected  in  a gas-holder,  as  shown  in  the  figure. 

The  most  convenient  mode  of  preparing  it  is  to  place  in 
a flask,  a,  Fig.  158,  a mixture  of  chlorate  of  potash  and 
peroxide  of  manganese  ; to  the  mouth  of  the  flask  a tube,  5, 
is  adapted  by  means  of  a tight  cork,  the  lower  end  of  the 

In  what  bodies  does  oxygen  occur?  Describe  its  preparation  from  red 
oxide  of  mercury,  from  peroxide  of  manganese,  and  from  chlorate  of  potash. 


180 


PREPARATION  OF  OXYGEN. 


tube  dipping  beneath  a jar  upon  the 
pneumatic  trough,  c.  On  raising 
the  temperature  of  the  flask  by  a 
spirit  lamp,  oxygen  gas  is  freely 
evolved.  The  peroxide  of  manga- 
nese takes  no  part  in  the  change,  but 
it  causes  the  decomposition  to  go  on 
at  a low  temperature,  and  the  gas 
is  more  rapidly  set  free.  The  change,  being  confined  to  the 
chlorate  of  potash,  is  therefore  expressed  as  follows: 


/f  O + CZ  O5 . . . . . . if  CZ  + Og ; 


that  is,  the  chlorate  of  potash,  at  the  temperature  in  ques- 
tion, has  its  atoms  disarranged,  resolving  itself  into  one 
atom  of  chloride  of  potassium  and  six  atoms  of  oxygen  gas. 

It  may  also  be  prepared  by  exposing  a mixture  of  bi- 
chromate of  potash  and  sulphuric  acid,  or  peroxide  of  man- 
ganese and  sulphuric  acid,  to  heat. 

Oxygen  gas  is  a colorless  body,  having  no  odor  nor  taste. 
It  is  a non-conductor  of  electricity,  and  a bad  refractor  of 
light.  It  is  a powerfully  electro-negative  element.  In 
specific  gravity  it  is  heavier  than  atmospheric  air ; for  the 
being  1-000,  oxygen  is  1-1026,  or,  according  to  some  chem- 
ists, 1-1111.  One  hundred  cubic  inches  weigh  about  34 
grains.  Its  atomic  weight  is  8-013,  hydrogen  being  taken 


What  are  its  leading  physical  properties  ? What  is  its  specific  gravity  ? 


PROPERTIES  OF  OXYGEN. 


181 


rs  1 000.  It  has  never  been  condensed  into  the  liquid 

To  a certain  extent  it  is  soluble  in  water,  one  hundred 
volumes  of  that  liquid  dissolving  about  four  of  the  gas,  a 
fact  of  considerable  importance  in  physiology,  as  it  is  upon 
the  oxygen  so  found  in  water  that  aquatic  animals  depend 
for  their  respiratory  process. 

On  litmus  water,  or  any  blue  vegetable  solution,  oxygen 
exerts  no  action,  as  it  is  easily  shown  by  agitating  Fig.  159. 
it  with  such  a solution  in  Hope’s  eudiometer  {Fig.  "" 
159);  but,  though  it  is  not  acid  itself,  when  it  unites 
with  a great  variety  of  bodies  it  gives  rise  to  power- 
ful acids,  and  from  this  circumstance  its  name  was 
derived.  Oxygen,  acid,  and  yevvetv,  to  gen- 

erate. 

The  most  important  qualities  of  atmospheric  air  I 
are  due  to  the  presence  of  oxygen  gas.  It  is  for  this  reason 
that  the  air  supports  combustion  and  respiration.  The 
powers  of  oxygen,  in  this  respect,  may  be  illustrated  by 
many  striking  experiments;  thus,  if  into  a jar  filled  with 
it,  a stick  of  wood,  with  a spark  of  fire  on  its  ex-  Fig.  i6o. 
tremity,  be  immersed,  it  bursts  out  at  once  into  a O 
flame,  burning  brilliantly. 

On  immersing  a lighted  taper  in  a jar  of  oxygen 
{Fig.  160),  the  light  becomes  of  a dazzling  white- 
ness, the  taper  wasting  rapidly  away  ; but  it  is  to  j 
be  observed  that  after  a time  the  combustion  de- 
clines, and  finally  the  light  is  extinguished. 

If  a piece  of  charcoal  of  bark  in  an  ignited  state  be 
placed  in  a bottle  of  oxygen,  the  combustion 
goes  on  with  great  activity,  a multitude  of 
sparks  being  thrown  off.  When  the  charcoal 
is  extinguished,  if  a little  lime-water  be  pour-  i 
ed  into  the  bottle  and  agitated  in  it,  the  lime- 
water  at  once  becomes  of  a milky  whiteness ; 
for  the  carbon,  during  the  combustion,  uniting 
with  the  oxygen,  produces  carbonic  acid  gas,  and  this  forms 
with  lime  a white  insoluble  precipitate,  the  carbonate  of 
lime. 


Can  it  be  liquefied  ? Is  it  soluble  in  water?  From  what  circumstance 
is  its  name  derived?  What  are  its  relations  in  the  ordinary  processes  of 
combustion  ? Describe  its  effect  on  a lighted  taper  and  on  ignited  char- 
coal. 


182 


COMBUSTION  IN  OXYGEN. 


A piece  of  India-rubber  set  on  fire,  and  immersed  in  oxy* 
gen  gas,  burns  with  the  emission  of  a dazzling  light.  And 
Fig.  162.  if,  upon  a small  stand,  some  burning  sulphur 
is  placed,  and  a j ar  of  oxygen  inverted  over  it, 
as  shown  in  Fig.  162,  the  light  which  is  emit- 
ted is  of  a splendid  blue  color,  and  the  smoke 
ascending  up  the  middle  of  the  jar,  and  falling 
in  curious  rings  down  its  sides,  affords  an  illus- 
tration of  the  manner  in  which  currents  are  ex- 
cited in  gases. 

But  it  is  not  alone  such  substances  as  wood, 
charcoal,  or  sulphur  which  will  burn  in  oxygen  gas  ; many 
Fig.  163.  bodies  commonly  regarded  as  incombustible  give 
rise  to  the  same  result.  If  a piece  of  steel  wire 
be  rolled  round  into  a spiral,  and  the  extremity  of 
it  be  dipped  in  melted  sulphur,  or  wrapped  round 
with  cotton,  so  as  to  afford  the  means  of  intro- 
ducing it  in  an  ignited  condition  into  oxygen  gas, 
the  combustion  is  at  once  communicated  to  the 
steel,  which  burns  in  a very  brilliant  manner, 
emitting  scintillations. 

164.  A stream  of  oxygen  from  a 

gas-holder,  being  thrown  upon 
an  iron  nail  made  red  hot  in  the 
flame  of  a spirit  lamp,  or  placed 
in  an  ignited  cavity  in  a piece 
of  charcoal,  causes  the  iron  to 
burn  with  rapidity,  emitting  a 
shower  of  sparks. 

When  a stream  of  electric 
sparks  is  passed  through  dry  and 
pure  oxygen,  a part  of  the  gas 
undergoes  a remarkable  change, 
its  chemical  affinities  being  for 
the  most  part  greatly  exalted,  and  a peculiar  phosphoric  odor 
communicated  to  it.  A similar  change  is  often  remarked 
in  oxygen  which  has  been  set  free  from  the  decomposition 
of  water  by  the  Voltaic  battery,  and  also  in  damp  atmos- 
pheric air  in  which  sticks  of  phosphorus  have  been  slowly 
oxydizing.  To  this  substance  the  name  of  Ozone  has  been 
given ; but  it  is  now  generally  regarded  as  an  allotropic 

What  is  its  effect  on  ignited  sulphur?  What  is  its  effect  on  an  ignited 
metal,  as  iron  or  steel  ? How  is  ozone  formed? 


COMBUSTION  IN  OXYGEN. 


183 


modification  of  oxygen,  and  that  this  substance,  like  carbon, 
phosphorus,  or  chlorine,  can  exist  in  two  different  conditions, 
an  active  and  a passive  state. 

Active  oxygen  or  ozone  readily  decomposes  iodide  of  po- 
tassium, sulphate  of  manganese,  and  yellow  ferrocyanide  of 
potassium.  It  is  not  soluble  in  water,  is  destroyed  by  a heat 
of  140^,  and  by  contact  with  several  hydro-carbons. 


LECTURE  XL. 

Oxygen  continued. — Drummond's  Light. — Combustion 
of  Phosphoi'us. — Double  Change  arising  in  Combus- 
tion.— The  Lavoisierian  Doctrine. — Basic,  Indifferent, 
and  Acid  Oxides. — Physiological  Relations  of  Oxygen. 
— Supporters  of  Cornbustion.  — Nature  of  Flame. — 
Constancy  of  Heat  evolved. — Vegetable  Origin  of  Oxy- 
gen in  the  Air. 

If  a piece  of  lime  the  size  of  a peppercorn  be  placed  in 
the  flame  of  a spirit  lamp,  through  which  oxygen  gas  is  di- 
rected by  a blowpipe,  the  lime  phosphoresces  powerfully, 
emitting  a light  so  bright  that  the  eye  can  scarcely  bear  it. 
This  is  the  original  form  of  what  is  called  Drummond’s 
light.  The  light,  however,  is  still  brighter  when  the  oxy- 
hydrogen  blowpipe  is  employed. 

The  combustion  of  phosphorus  in  oxygen  165. 

gas  constitutes  one  of  the  most  brilliant  exper- 
iments. A piece  of  lighted  phosphorus  im- 
mersed in  an  atmosphere  of  this  gas,  burns 
with  the  evolution  of  a prodigious  amount  of 
light  and  heat.  Fig.  165.  Notwithstanding 
the  production  of  dense  flakes  of  phosphoric 
acid  intervening  between  the  eye  and  the 
burning  mass,  the  light  is  very  brilliant. 

When  any  combustible  substance  is  burned  in  oxygen  gas, 
two  striking  phenomena  are  exhibited : a change  in  the 
combustible,  and  a change  in  the  oxygen.  A fragment  of 


What  are  its  properties  ? What  is  the  original  form  of  the  Drummond 
light  ? What  are  the  phenomena  of  the  combustion  of  phosphorus  in  oxy- 
gen ? In  these  combustions,  what  changes  take  place  in  the  oxygen  and  in 
the  burning  body  ? 


184 


THE  OXIDES. 


ignited  charcoal  rapidly  wastes  away,  and  the  surrounding 
gas  loses  its  power  of  supporting  combustion.  Until  the 
time  of  Lavoisier,  it  was  generally  supposed  that  burning 
was  due  to  the  escape  of  a certain  principle,  called  phlogis- 
ton, from  bodies,  but  he  showed  that  in  all  these  cases  there 
is  no  loss  of  weight,  and  that,  in  reality,  the  combustion  is 
due  to  the  oxygen  uniting  with  the  burning  body ; and  if 
care  be  taken  to  collect  all  the  products  of  the  action,  their 
united  weight  will  be  exactly  that  of  the  oxygen  and  com- 
bustible conjointly.  Lavoisier  was  disposed  to  believe,  that 
in  all  cases  of  true  burning  the  presence  of  oxygen  is  indis- 
pensable, an  idea  now  known  to  be  erroneous ; for  light 
and  heat  are  evolved  in  all  cases  where  chemical  action  is 
going  on  with  great  intensity,  no  matter  what  may  be  the 
substances  which  happen  to  be  present. 

In  the  Lavoisierian  system  of  chemistry,  oxygen  was  re- 
garded as  being  the  essential  supporter  of  combustion  ; and 
as,  in  many  instances,  it  gives  rise  to  the  production  of 
acids,  it  was  also  regarded  as  the  essential  principle  of  acid- 
ity ; and  from  this  circumstance  its  name  was  derived,  as 
has  been  already  said.  But  so  far  from  every  acid  contain- 
ing oxygen  gas,  it  is  now  well  known  that  there  are  many 
from  which  this  principle  is  wholly  absent.  If  any  sub- 
stance in  particular  deserves  the  name  of  “ the  acid  form- 
er,” it  is  hydrogen,  for  it  is  doubtful  whether  any  powerful 
acid  exists  which  does  not  contain  hydrogen.  Basic  sub- 
stances, on  the  contrary,  are  characterized  by  containing 
oxygen. 

To  the  compounds  which  arise  from  the  union  of  oxy- 
gen with  other  bodies,  the  generic  designation  of  oxides  is 
given,  and  of  them  we  have  three  classes.  1st.  Basic  ox- 
ides. 2d.  Indifferent  oxides.  3d.  Acids.  If  M represents 
an  electro-positive  body,  the  basic  oxides  are  constituted  as 
follows : 

MO  . . . Protoxide,  usually  the  most  povferful  base., 

JlfgOa  . . . Sesquioxide,  a weaker  base. 

MO^  . . . Deutoxide,  a still  weaker  base. 

M2O  . . . Suboxide,  “ “ 

The  oxides  of  manganese  furnish  a good  example  of  the 
three  classes  : 


What  was  Lavoisier’s  theory  of  combustion?  What  is  the  relation  of 
oxygen  to  acid  and  basic  bodies  ? What  is  the  generic  designation  for  its 
compounds  ? What  are  the  three  classes  of  compounds  which  it  yields  ? 


PHYSIOLOGICAL  RELATIONS  OF  OXYGEN.  185 


Protoxide  of  manganese  . 

MnO 

Sesquioxide  “ 

Mn^O-. 

Deutoxide  “ 

. MnO  2 

Manganic  acid  . 

MnO  2 

Hypermanganic  acid 

Mn^O: 

Basic  oxides. 
Indifferent  oxide. 
Acids. 


From  which  it  may  be  inferred  that,  in  a family  of  ox- 
ides of  an  electro-positive  body,  the  most  powerful  base  is 
that  containing  one  atom  of  oxygen,  and  that,  as  the  quan- 
tity of  this  element  increases,  indifferent  bodies  may  be  form- 
ed ; that  is  to  say,  those  in  which  neither  the  basic  nor  acid 
qualities  are  well  marked,  and  on  a still  farther  increase 
acids  are  produced.  In  this  respect,  therefore,  the  original 
idea  of  Lavoisier  respecting  the  character  of  oxygen  is  to 
some  extent  substantiated. 

In  its  physiological  relations  oxygen  is  a most  interesting 
body.  It  is  for  the  purpose  of  introducing  this  element  to 
the  interior  of  the  system  that  the  respiratory  mechanism 
of  animals  is  devoted — a mechanism  which  differs  according 
to  their  mode  of  life,  the  gills  of  a fish  and  the  lungs  of  a 
man  having  the  same  ulterior  object.  If  two  jars  are  taken, 
one  full  of  atmospheric  air  and  one  of  oxygen  gas,  and 
small  animals  placed  beneath  each,  it  will  be  found  that  in 
the  latter  those  animals  survive  much  longer  than  in  the 
former.  The  gas  introduced  into  the  system  arterializes  the 
blood,  and,  eventually  uniting  with  carbon  and  hydrogen, 
keeps  up  the  temperature  to  a standard  point,  which,  in  the 
human  mechanism,  is  about  98°  F.’  Oxygen  gas,  there- 
fore, is  emphatically  the  supporter  of  respiration. 

The  terms,  supporter  of  combustion  and  combustible  body, 
formerly  much  used  by  chemical  writers,  are  expressive  of 
an  erroneous  idea.  No  substance  is  in  itself  a supporter  of 
combustion,  nor  is  any  one  intrinsically  a combustible  body. 
If  a jet  of  hydrogen  burns  in  an  atmosphere  of  oxygen,  so 
also  will  a jet  of  oxygen  burn  in  an  atmosphere  of  hydro- 
gen gas.  In  fact,  both  bodies  are  equally  engaged  in  pro- 
ducing the  result,  combustion  only  taking  place  upon  their 
mutual  surface  of  contact.  The  division  in  question  has 
arisen  from  the  circumstance  that  the  most  familiar  in- 
stances of  combustion  we  witness  take  place  in  the  atmos- 


In  the  basic,  the  indiiferent,  and  the  acid  group,  what  is  the  general  rela 
tion  of  the  oxygen?  For  what  purpose  is  oxygen  introduced  into  the  sys 
tem  ? Why  is  it  to  be  regarded  as  the  supporter  of  respiration  ? Is  the 
division  of  bodies  into  combustibles  and  supporters  of  combustion  a cor- 
rect one  ? 


18G 


STRUCTURE  OF  FLAME. 


phere,  which  owes  all  its  active  qualities  to  the  presence  of 
oxygen. 

Combustion  takes  place  only  at  those  points  where  the 
uniting  substances  are  in  contact.  The  flame  of  a candle 
is  not  incandescent  throughout,  hut  is  a mere 
superficies  or  luminous  shell,  with  a dark  interior. 
In  such  a flame  several  distinct  parts  may  he 
traced.  Around  the  wick,  a.  Fig.  166,  at  the 
points  i ^,  the  light  is  of  a blue  color ; for  here 
the  air  being  in  excess,  the  combustion  is  perfect. 
From  this  toward  c the  combustible  matter  pre- 
dominates, and  the  light  is  most  intense.  A 
faint  exterior  cone,  e e,  surrounds  the  more  lu- 
minous portion,  but  the  interior  at  b is  totally 
dark,  as  may  be  proved  by  placing  a piece  of  mica 
or  glass  upon  the  flame.  It  is  probable  that  the 
light  arises  chiefly  from  the  ignition  of  solid  matter,  for  in- 
candescent gases  are  only  faintly  luminous.  The  hydrogen 
of  the  flame  is  first  burned,  and  for  a moment  carbon  is  set 
free  in  the  solid  form  at  a very  high  temperature,  its  oxy- 
dation  instantly  ensuing. 

A given  weight  of  a combustible  body,  when  burned, 
will  always  furnish  a constant  amount  of  heat.  If  an  ounce 
of  carbon  be  burned  in  a few  moments  in  pure  oxygen  gas, 
the  amount  of  heat  disengaged  appears  to  be  very  great ; 
though,  in  reality,  it  is  the  same  that  would  finally  be  yield- 
ed by  a slower  combustion  in  atmospheric  air.  So,  too, 
metallic  iron  becomes  quite  hot  when  burned  in  oxygen, 
because  the  combination  goes  forward  with  great  rapidity  ; 
but  precisely  the  same  amount  would  be  yielded  in  the  slow 
oxydation  of  rusting,  though  in  the  latter  instance  it  might 
take  years  for  the  completion  of  the  process.  This  is  a fact 
of  great  physiological  importance. 

We  have  just  said  that  atmospheric  air  owes  all  its  ac- 
tivity to  the  presence  of  oxygen,  and  as  there  are  inces- 
santly combustive  processes  going  on,  the  tendency  of  which 
is  to  remove  oxygen  from  the  air  and  generally  replace  it 
with  carbonic  acid — a result,  also,  which  ensues  from  res- 
piration, in  every  part  of  the  earth  where  animals  are  found 
— -it  would  appear  a necessary  consequence  that  the  consti- 

What  is  the  nature  of  flame  ? "Why  do  the  different  regions  of  a lamp 
flame  differ  in  luminous  power  ? Is  there  any  difference  in  the  amount  of 
beat  evolved  in  rapid  and  in  slow  combustions  ? ^ 


ORIGIN  OF  OXYGEN  IN  NATURE. 


187 


tut  ion  of  the  air  should  incessantly  change,  the  amount  of 
oxygen  declining  and  that  of  carbonic  acid  increasing.  But 
in  this  respect  the  vegetable  world  exerts  an  opposite  ten- 
dency to  the  animal ; for,  under  the  influence  of  the  light 
of  the  sun,  plants  decompose  carbonic  acid  gas,  setting  free 
its  oxygen,  and  appropriating  the  carbon  to  their  own  uses. 
This  beautiful  fact  was  originally  discovered  by  Priestley, 
who  found,  that  if  some  green  leaves  were  placed  Ft£r.  167. 
in  a bottle,  as  in  Fig.  167,  containing  carbonic  acid 
gas,  or,  what  is  more  convenient,  water  holding  that 
substance  in  solution,  so  long  as  the  sun  does  not 
shine  on  them,  no  action  is  perceived  ; but  if  the 
bottle  be  set  in  the  sun,  bubbles  of  gas  are  rapidly 
disengaged  from  the  leaves,  and,  rising  up  through 
the  water,  collect  in  the  upper  part  of  the  bottle,  and,  if  ex- 
amined, prove  to  be  very  rich  in  oxygen. 

A question  has  arisen  as  to  what  principle  the  remark- 
able decomposition  is  due.  I have  proved,  by  causing  it  to 
take  place  in  the  prismatic  spectrum,  that  it  is  due  to  the 
yellow  ray  of  light. — {Phil.  Mag,j  Sept.,  1843.) 


LECTUEE  XLI. 

Hydrogen. — Preparation  and  Properties  of  Hydrogen. — 
Relations  to  Respiration. — Combustibility. — Its  Light- 
ness.— Explosive  Combustion. — Production  of  Water. 
— Oxhydrogen  Blow-pipe. 

HYDROGEN.  H=l. 

If  a piece  of  potassium  be  wrapped  in  paper  and  rapid- 
ly immersed  beneath  an  inverted  jar  at  the  water-trough, 
violent  reaction  soon  sets  in,  a gas  collects  in  the  upper  part 
of  the  jar,  and  the  potassium,  oxydizing,  dissolves  in  the 
water.  The  gas  so  produced  is  hydrogen,  and  the  decom- 
position is  very  simple,  as  shown  in  the  following  symbols  : 
HO  + K...z=z...KO  II; 

that  is,  water  acted  upon  by  metallic  potassium  yields  ox- 
ide of  potassium  and  hydrogen  gas. 

What  are  the  causes  which  tend  to  diminish  the  amount  of  oxygen  in  the 
air  ? By  what  agency  is  this  tendency  compensated  ? What  is  the  prmci, 
pie  of  the  decomposition  of  water  by  potassium  ? 


188 


HYDROGEN  GAS. 


In  practice  more  economical  processes  are  resorted  to. 
Like  potassium,  metallic  zinc  can  decompose  water  at  or- 
dinary temperatures,  but  there  is  this  difference  between 
them,  that  while  the  oxide  of  potassium  is  very  soluble  in 
water,  the  oxide  of  zinc  is  nearly  insoluble.  A plate  of  pol- 
ished zinc  immersed  in  water  does  not,  therefore,  give  rise 
to  a stream  of  gas,  for  the  moment  the  incipient  action  has 
set  in  it  ceases,  the  zinc  becoming  covered  with  an  imper- 
vious pellicle  of  oxide,  which  cuts  off  farther  contact  with 
the  water. 

If,  however,  we  add  any  acid  substance  which  can  form 
with  the  oxide  a salt  soluble  in  water,  the  action  will  go 
on  continuously,  because  the  zinc  can  now  expose  a clear 
metallic  contact.  Such  a substance  is  sulphuric  acid.  To 
make  hydrogen,  therefore,  we  take  a bottle,  a. 
Fig.  168,  and  having  placed  in  it  some  strips 
of  zinc,  add  sufficient  water  to  cover  them  en- 
tirely, and  then  adjust  to  the  mouth  of  the  bot- 
tle a cork,  through  which  two  tubes,  b and  c, 
pass.  Through  b sulphuric  acid  is  poured  in 
such  a quantity  as  to  excite  a brisk  but  not  too 
violent  effervescence,  and-the  gas,  as  it  gener- 
ates, passes  out  through  c.  It  is  absolutely 
necessary  to  allow  a quantity  of  the  gas  to  escape  before 
attempting  to  collect  it,  because  the  first  portions  form,  with 
the  air  in  the  upper  part  of  the  bottle,  an  explosive  mixture ; 
but  as  soon  as  it  is  judged  that  the  air  is  all  expelled,  we 
may  proceed  to  collect  the  gas  ; and  whenever  the  produc- 
tion slackens,  if  more  acid  be  added  through  the  funnel  tube, 
by  the  supply  may  be  kept  up. 

Hydrogen  gas  is  a transparent  and  colorless  body,  which 
exerts  a powerful  refracting  action  on  light.  When  pure, 
it  has  neither  taste  nor  smell,  but,  as  thus  obtained,  it  has 
a peculiar  odor.  It  is  the  lightest  body  in  nature,  its  spe- 
cific gravity  being  0*0694.  One  hundred  cubic  inches  of  it 
weigh  2*1  grains.  The  weight  of  its  atom  is  taken  as  the 
standard  of  comparison  of  other  atomic  weights  in  this  book ; 
it  is  therefore  = 1 . It  exerts  no  action  on  vegetable  colors, 
and  is  very  sparingly  soluble  in  water,  one  hundred  cubic 
inches  of  that  liquid  dissolving  about  one  and  a half  of  hy- 
drogen gas.  Hydrogen  has  never  been  liquefied. 

What  is  the  reason  that  zinc  can  not  decompose  water  alone  ? How  may  hy% 
drogen  gas  be  made  by  the  aid  of  zinc  ? What  are  the  properties  of  this  gas  ? 


Fig.  168. 


^ PROPERTIES  OF  HYDROGEN. 


189 


Fig.  169. 


As  respects  the  animal  economy,  hydrogen  gas  does  not 
exert  any  directly  deleterious  effect ; and  although  it  can 
not,  of  course,  carry  on  the  functions  of  respiration,  which 
are  acts  of  oxydation,  yet  it  can,  for  a short  space,  be  intro- 
duced into  the  lungs  with  impunity.  If  a person  whose 
lungs  are  inflated  with  it  attempts  to  speak,  his  voice  resem- 
bles the  feeble  and  shrill  voice  of  a child.  This  arises  from 
the  small  density  of  hydrogen  ; a bell  rung  in  this  gas  emits 
almost  as  feeble  a sound  as  if  rung  in  a vacuum. 

One  of  the  most  striking  peculiarities  of  hydrogen  is  its 
great  inflammability  in  contact  with  ox- 
ygen. If  ajar,  Fig.  169,  with  a stop- 
cock at  its  upper  extremity,  be  filled 
with  hydrogen,  and  then,  being  depress- 
ed in  the  water  of  the  trough,  the  cock 
opened  and  a light  brought  near  the  hy- 
drogen as  it  escapes,  it  takes  fire  F^g.no. 
at  once,  burning  with  a pale  yel- 
low flame.  Or  if  to  the  mouth  of 
a bottle  containing  the  materials 
for  generating  hydrogen,  a.  Fig.  170,  a cork,  through 
which  a glass  tube,  5,  is  passed,  be  adjusted,  and 
after  allowing  the  air  in  the  bottle  to  be  displaced,  a 
light  be  applied  to  the  issuing  gas,  it  takes  fire  and 
burns  in  the  same  manner  ; an  experiment  commonly  de- 
scribed as  the  philosophical  candle. 

The  following  experiment  proves  three  facts  at  the  same 
time  : 1.  The  great  lightness  of  hydrogen;  2.  Its  Fig.iii. 
inflammability  ; 3.  That  it  is  not  a supporter  of 
combustion.  A jar,  a.  Fig.  171,  is  to  be  filled 
with  hydrogen  at  the  water-trough,  and  then,  be- 
ing lifted  in  the  air  with  its  mouth  downward,  a 
taper,  placed  on  a bent  wire,  is  carried  into  its  in- 
terior. As  the  taper  passes  the  mouth  of  the  jar  : 
there  is  a feeble  explosion,  and  the  hydrogen,  taking ' 
fire,  burns  with  a pale  flame  ; but  as  soon  as  it  is  immersed 
in  the  atmosphere  of  the  gas  the  taper  is  extinguished.  It 
may,  however,  be  relighted  as  it  is  brought  out  of  the  jar 
at  the  burning  hydrogen,  and  this  may  be  repeated  several 
times  in  succession.  The  combustibility  of  the  gas  and  its 

What  are  its  relations  to  respiration?  How  may  its  combustiliility  ho 
demonstrated  ? How  may  its  inflammability,  its  nou-supporting  power,  and 
its  lightness  be  simultaneously  illustrated  ? 


190 


COMBUSTION  OP  HYDROGEN. 


quality  of  not  supporting  combustion  are  obvious  enough, 
and  its  lightness  is  proved  by  the  fact  that  it  does  not  flow 
out  of  the  open  mouth  of  the  jar,  which  it  would  do  at  once 
if  it  were  heavier  than  atmospheric  air. 

The  application  of  hydrogen  to  aerostatic  purposes  is 
founded  upon  its  small  specific  gravity.  This  property  is 
very  distinctly  illustrated  by  filling  an  India-rubber  gas-bag 
with  hydrogen,  and  having  attached  to  the  stop-cock,  a, 
Fig,  172.  Fig,  172,  which  closes  it,  a common  earth- 


If,  in  a strong  brass  vessel,  a.  Fig.  173,  we  place  a mix- 
Fig.  173.  ture  of  hydrogen  and  atmospheric  air  in  equal 


lent  explosion  takes  place,  the  hydrogen  burning  instanta- 
neously with  the  atmospheric  oxygen,  and  giving  rise  to  the 
production  of  water.  • 1"^  ' 

Musical  sounds  originate  in  vibratory  movements  com- 
municated to  the  air.  If  the  flame  of  a philosophical  can- 
die  is  covered  by  a wide  glass  tube,  as,  for  example,  the 
^ neck  of  a broken  retort,  an  intensely  powerful  sound  is 
f emitted.  This  arises  from  the  circumstance  that  the 
I hydrogen  burns  in  the  tube,  giving  rise  to  a series  of 
I small  explosions,  which  follow  each  other  with  rapidity, 

I and  these  explosions  throw  the  air  in  the  tube  into  a 
m vibratory  state.  According  as  the  tube  is  raised  or 

II  lowered,  these  explosions  occur  with  different  degrees 
V of  rapidity,  sometimes  producing  a clattering  sound,  and 
“ then  a pure  musical  note. 

Whatever  may  be  the  circumstances  under  which  hydro- 
gen burns,  whether  quietly,  as  in  the  philosophical  candle, 
or  with  trivial  explosions,  as  in  this  tube,  or  with  a violent 
detonation,  as  in  the  preceding  experiment,  the  uniform  pro- 


To  what  purpose  is  hydrogen  applied  in  consequence  of  its  lightness  ? 
How  may  this  be  illustrated  on  a small  scale  ? When  mixed  with  oxygen 
or  air,  and  an  electric  spark  passed  through  it,  what  is  the  result  ? Under 
what  circumstances  will  the  flame  of  hydrogen  emit  a musical  sound  ? 


en- ware  tobacco-pipe,  5,  by  dipping  the  pipe 
in  a solution  of  soap,  bubbles  may  be  blown. 
These  rise  through  the  air  with  rapidity ; 
and  if  a lighted  taper  is  brought  near  them 
as  they  are  ascending,  the  hydrogen  takes 
fire  and  burns  with  a yellowish  flame. 


volumes,  and,  having  inserted  the  cork,  c, 
|(?  tightly,  pass,  by  the  aid  of  the  ball  and  wire, 
b,  an  electric  spark  through  the  gas,  a vio- 


OXYHYDROGEN  BLOW-PIPE. 


191 


duct  of  the  combustion  is  water.  During  the  combination 
of  these  elementary  bodies  with  each  other  a very  great 
amount  of  heat  is  given  out,  for  hydrogen  combines  with 
eight  times  its  own  weight  of  oxygen,  a greater  proportion 
than  is  met  with  in  the  case  of  any  substance  whatever. 
Advantage  is  taken  of  this  in  the  construction  of  the  oxy- 
hydrogen  blow-pipe,  an  instrument  invented  by  Dr.  Hare, 
which  furnishes  us  with  the  most  efficient  means  of  obtain- 
ing a high  temperature.  There  are  sev-  Fig.  175. 
eral  different  forms  of  this  blow-pipe ; in 
some  the  gases  are  mixed  in  the  proper 
proportions  in  a strong  receiver,  and  set 
on  fire  after  passing  through  a Hemming’s 
safety  tube.  But  it  is  better  to  keep  them 
in  separate  reservoirs,  and  conduct  them 
to  a common  jet,  where  they  may  simul- ; 
taneously  mix  and  be  burned,  as  is  shown  in  Fig.  175,  where 
O is  the  oxygen  reservoir,  H the  hydrogen,  a h the  flexible 
lead  pipes,  leading  to  a common  jet,  c,  at  which  the  gases 
are  set  on  fire.  By  this  instrument  substances  perfectly  in- 
fusible in  a common  furnace  melt  at  once.  The  intensity 
of  the  heat  of  this  blow-pipe  depends,  to  a great  extent,  on 
the  fact  that,  unlike  ordinary  flames,  the  oxyhydrogen  flame 
is,  as  it  were,  solid ; that  is,  incandescent  throughout  all  its 
parts. 

In  its  general  relations,  hydrogen  possesses  so  many  of  the 
properties  of  the  metallic  class,  that  there  is  every  reason 
to  believe  it  is,  in  reality,  a metal.  The  facts  of  its  aerial 
form  and  transparency  can  scarcely  be  regarded  as  of  any 
weight  against  this  conclusion,  for  the  vapor  of  mercury 
possesses  a similar  aspect. 


What  is  the  uniform  production  of  its  combustion?  Why  is  so  much 
heat  evolved  in  the  burning  of  a mixture  of  oxygen  and  hydrogen  ? De- 
scribe Hare’s  compound  blow-pipe.  What  is  the  peculiarity  of  the  flame  ? 
To  what  class  of  bodies  does  hydrogen  probably  belong  ? 


192 


WATER. 


LECTURE  XLII. 

Water. — Hydrogen  Acids. — Water. — Its  Properties  — 
Compressibility. — Constitution  of  Water.— Syntheses 
of  Water. — By  Spongy  Platinum. — Determination  of 
its  Composition  by  Weight. — Analysis  of  Water. — 
..Chemical  Relations  of  Water. — Water  of  Crystalliza- 
tion and  Saline  Water. — Acts  as  a basic,  indifferent, 
and  acid  Body. — Purification. — Deutoxide  of  Hydro- 
gen. 

WATER.  270  = 9013. 

Hydrogen  unites  with  all  the  electro-negative  substances, 
and,  with  many  of  the  more  prominent  ones,  forms  strong 
acids.  The  hydrogen  acids  of  chlorine,  bromine,  iodine,  and 
fluorine  are  all  constituted  upon  the  same  type,  in  which,  if 
the  electro-negative  radical  be  represented  by  R,  we  have 
HR. 

But  with  oxygen,  instead  of  an  acid,  a neutral  body  results. 
This  body  is  common  water. 

Water,  as  will  be  presently  proved,  results  from  the  union 
of  oxygen  and  hydrogen,  one  atom  of  each  of  these  elements 
combining  to  form  one  atom  of  water.  It  is,  therefore,  a 
binary  compound.  Its  symbol  is 
HO. 

By  volume,  it  consists  of  two  of  hydrogen  united  with 
one  of  oxygen ; by  weight,  one  part  of  hydrogen  united  with 
eight  of  oxygen.  These  statements  correspond  with  the 
first,  because  the  hydrogen  atom  is  twice  the  volume  of  that 
of  oxygen ; and  the  weight  of  an  atom  of  oxygen  is  eight 
times  that  of  hydrogen. 

Water  is  a colorless  and  tasteless  body.  It  freezes  at  32° 
F.,  and  boils  at  212°  F.  Its  specific  gravity  is  I’OOO,  be- 
ing the  standard  of  comparison  of  all  other  liquid  and  solid 
bodies.  The  specific  gravity  of  its  vapor,  steam,  compared 
with  atmospheric  air,  is  0-6201.  It  is  a compressible  and 
elastic  substance.  One  cubic  inch  of  it  at  62°  weighs 
252-45  grains. 

When  hydrogen  unites  with  electro-negative  substances,  what  class  of 
bodies  arise  ? What  is  the  constitution  of  water  ? What  are  the  proper 
ties  of  water  ? 


COMPRESSIBILITY  OF  WATER. 


193 


Fig.  176.  The  compressibility  of  water  is  at  once  demon- 
strated and  measured  by  an  instrument  invented 
by  (Ersted,  and  represented  in  Fig.  176.  It  con- 
sists essentially  of  a strong  glass  cylinder,  a a,  fill- 
ed with  water,  upon  which  a powerful  pressure 
can  be  exerted  by  means  of  a piston  driven  by  a 
screw,  b.  In  this  cylinder  of  water  a gage,  repre- 
sented on  a larger  scale  by  Fig.  177,  is  placed. 
The  gage  consists  of  a reservoir,  e,  prolonged  into 
a fine  tube,  f;  there  is  also  a scale  annexed.  Fig.vn. 
The  reservoir  and  part  of  the  tube  are  filled 
j [_  with  water,  and  a small  column  of  quicksil- 
JSIJL  ver,  Xj  indicates  the  point  on  the  tube  to 
t - which  the  water  reaches.  The  pressure  ex- 
erted is  measured  by  an  air-gage,  d.  ^ 

If  now  this  instrument  be  placed  in  the  strong 
glass  cylinder,  as  seen  in  Fig.  176,  and  pressure  ex- 
erted by  turning!  the  screw,  the  air  in  the  gage, 
contracts,  and  indicates  the  amount  of  that  pressure ; 
at  the  same  time,  the  small  column  of  mercury,  x, 
descends  in  the  tube,  showing  that  the  water  con- 
tracts, and  measuring  its  amount.  On  turning  thei^ 
screw  the  other  way,  so  as  to  relieve  the  apparatus 
of  pressure,  the  air-gage  comes  back  to  its  original  point,  and 
the  mercury  in  the  fine  tube  ascends  again.  It  is  obvious, 
therefore,  that  by  this  instrument  we  measure  the  compress- 
ibility of  the  water  contained  in  the  reservoir,  €,  due  allow- 
ance being  made  for  the  minute  amount  of  contraction  which 
the  glass  of  which  e is  made,  and  which  is  pressed  178. 
equally  on  its  inside  and  outside,  undergoes ; and  also 
for  variations  of  temperature.  (Ersted’s  instrument  _ 
shows  that  water  is  compressed  ^ 
ume  for  each  atmosphere  of  pressure.  " 

The  constitution  of  water  was  first  clearly  proved 
by  Mr.  Cavendish.  It  can  be  illustrated  in  a vari- 
ety of  ways.  Thus,  if  over  a jet  of  burning  hydro- 
gen a cold  glass  bell  be  suspended,  as  in  Fig.  178,  it 
becomes  soon  covered  with  a misty  dew,  and,  if  the 
experiment  be  prolonged,  drops  of  liquid  finally  trickle  down 
the  sides,  and  may  be  caught  in  a vessel  placed  to  receive 

Describe  CErsted’s  instrument  for  proving  its  compressibility.  What  is 
the  amount  of  its  compressibility?  How  may  its  composition  be  synthet- 
ically illnstrnted  ? 

I 


194 


SYNTHESIS  OP  WATER. 


them.  When  examined,  this  liquid  is  found  to  he  water. 
It  has  arisen  from  the  union  of  the  hydrogen  with  atmos- 
pheric oxygen. 

If  in  a vessel  over  the  mercurial  trough  twenty  measures 
of  pure  hydrogen  are  added  to  ten  measures  of  pure  oxygen, 
and  a small  pellet  of  spongy  platinum  passed  up  through 
the  quicksilver,  union  between  the  two  gases  rapidly  takes 
place,  so  that  it  is  usual,  in  order  to  moderate  its  action,  to 
mix  the  spongy  platina  previously  with  a little  pipe  clay. 
As  the  gases  unite,  the  mercury  rises,  until  at  last  they 
have  totally  disappeared.  This  beautiful  experiment  shows 
that  the  constitution  of  water  by  volume  is  2 of  hydrogen 
to  1 oxygen,  as  has  already  been  said. 

The  composition  of  water  by  weight  was  determined  by 
Berzelius  as  follows : Let  a flask,  a,  Fig.  1 79,  containing 


zinc  and  dilute  sulphuric  acid,  be  connected  by  a bent  tube, 
5,  with  another  tube,  d,  containing  chloride  of  calcium  ; the 
hydrogen  which  is  consequently  evolved  from  the  flask  de- 
posits any  small  quantity  of  water  it  may  be  contaminated 
with  in  the  bulbs  c c,  and  then  passing  through  the  chloride 
of  calcium  tube,  d,  is  made  perfectly  dry.  The  tube  d is 
connected  with  a tube  of  hard  glass,  on  which  a bulb,  e,  i? 
blown.  This  bulb  is  filled  with  a known  weight  of  oxide 
of  copper,  which  can  be  raised  to  a red  heat  by  means  of  a 
spirit  lamp,  h ; and  as  the  dry  hydrogen  passes  over  the  ig- 
nited oxide,  it  reduces  it,  forming  with  its  oxygen  water,  and 
leaving  pure  metallic  copper.  The  water  thus  produced 
is  partially  collected  in  the  bulb  /,  and  the  rest  of  it  is  de- 
tained by  a second  chloride  of  calcium  tube,  g. 

How  may  the  constitution  of  water  be  proved  synthetically  by  spongjf 
platinum  ? Describe  the  methqd  of  Berzelius  for  determining  the  compo* 
sitjon  of  water  by  weight. 


ANALYSIS  OF  WATER. 


195 


Fig.  180. 


If,  therefore,  we  weigh  the  tube  e before  and  after  the 
experiment,  in  the  latter  instance  its  weight  will  be  less 
than  the  former,  the  difference  being  due  to  the  amount  of 
oxygen  which  has  been  removed.  If,  also,  we  weigh  the 
tubes  f and  g before  and  after  the  experiment,  in  the  lat- 
ter case  they  weigh  more  than  in  the  former,  the  differ- 
ence being  the  weight  of  water  produced.  Thus  it  will  be 
found  that  for  every  eight  grains  that  the  oxide  of  copper 
has  lost,  nine  grains  of  water  have  been  produced,  showing 
that  the  constitution  of  water  is  by  weight  8 of  oxygen  to  1 
of  hydrogen. 

The  composition  of  water  may  also  be 
proved  analytically  as  well  as  synthetically. 

It  has  been  already  stated  that  this  can  be 
done  by  the  Voltaic  battery  in  a very  satis- 
factory manner.  An  apparatus  suited  for 
this  purpose  is  shown  in  Fig.  180.  The 
polar  wires  of  the  battery  enter  the  sides  of 
a globular  glass  vessel  full  of  water,  and 
over  their  terminations  tubes  are  inverted  in 
which  to  receive  the  gases.  The  hydrogen 
is  double  the  volume  of  the  oxygen. 

Another  form  of  the  same  apparatus  is 
seen  in  Fig.  181.  In  a bent  tube  full  of  n\ 
water,  the  platina  wires,  N P,  are  intro- 
duced by  means  of  corks.  On  the  current 
passing,  oxygen  is  collected  in  one  of  the 
branches  of  the  tube  and  hydrogen  in  the 
other. 

Lavoisier  determined  the  composition 
of  water  by  passing  its  vapor  over  pieces 
of  iron  made  red  hot  in  a tube.  Thus, 
if  from  the  retort,  a,  Fig.  182,  containing 
boiling  water,  steam  is  passed  through  a red-hot  iron  tube, 
c c,  filled  with  turnings  of  iron,  or  iron  wire,  decomposition 
takes  place,  black  oxide  of  iron  forming,  and  hydrogen  gas 
escaping  by  the  tube,  /,  into  the  gas-holder,  m n. 

The  chemical  relations  of  water  are  of  the  utmost  im- 
portance. It  exerts  a more  general  solvent  action  than  any 
other  liquid  known,  holding  in  solution  gaseous  and  solid 
substances,  acids,  alkalies  and  salts.  As  respects  gaseous 

How  may  the  analysis  of  water  be  effected  ? Describe  the  principle  of 
Laroisier’s  analysis  of  water. 


DECOMPOSITION  OF  WATER. 


106 


182. 


bodies,  the  quantity  which  water  will  take  up  is  to  a con- 
siderable extent  dependent  on  pressure,  and  in  the  case  of 
salts,  an  increase  of  temperature  very  frequently  increases 
its  solvent  power.  Salt-crystals  sometimes  contain  a very 
Fig.  183.  considerable  quantity  of  it,  as  is  shown  in  the 
case  of  common  alum,  of  which,  if  a mass  be 
put  upon  a . red-hot  brick,  Fig.  183,  it  melts  in 
its  own  water  of  crystallization,  and,  after  a 
great  quantity  of  steam  is  thrown  off,  a dry  res- 
idue remains.  Crystals  often  contain  water 
in  two  different  states,  one  portion  known  under  the  name 
of  water  of  crystallization,  which  may  generally  be  expell- 
ed by  a moderate  heat ; another  portion  known  as  saline 
water,  which  is  with  much  more  difficulty  driven  off.  In 
the  works  on  chemistry,  the  formulae  are  constructed  so  as 
to  indicate  these  different  conditions  of  the  water : Aq  (aqua) 
being  the  symbol  for  the  water  of  crystallization,  and  HO 
for  the  saline  water  ; thus, 

FeO  + /SO3  + HO  + 

is  the  symbol  for  green  vitriol,  which  is  therefore  a sulphate 
of  the  protoxide  of  iron,  with  one  atom  of  saline  water  and 


How  does  water  compare  with  other  bodies  as  respects  solvent  power  ? 
What  is  meant  by  water  of  crystallization  and  saline  water?  How  is  this 
difference  indicated  in  formulae  ? 


DEUTOXIDE  OP  HYDROGEN. 


m 


six  of  water  of  crystallization.  The  latter  is  easily  driven 
off  by  heat,  hut  the  former  only  at  high  temperatures^  or  by 
being  replaced  by  some  other  body. 

Water  unites  with  many  acids  with  great  energy.  If 
mixed  with  sulphuric  acid,  and  a thermometer  immersed, 
the  temperature  will  run  up  rapidly  to  above  212°.  With 
basic  bodies,  the  same  results  may  be  obtained  as  when 
quicklime  is  sprinkled  with  water,  or  potash  and  soda  dis 
solved  in  it:  toward  acids  water  acts  as  a base;  toward 
bases  it  acts  as  an  acid ; and  toward  salts  as  an  indifferent 
body. 

As  found  in  nature,  water  is  always  impure.  Kain-water 
and  melted  snow  contain  the  various  soluble  gases  which 
are  in  the  air ; spring,  river,  well,  and  mineral  waters  the 
soluble  bodies  of  the  strata  through  which  they  have  flow- 
ed ; from  these  it  can  only  be  purified  by  the  process  of  dis- 
tillation. 

DEUTOXIDE  OF  HYDROGEN.  HO^  = 17'013. 

There  is  another  compound  of  hydrogen  and  oxygen,  the 
deutoxide  of  hydrogen.  It  contains  twice  the  amount  of 
oxygen  found  in  water,  and  is  characterized  by  a remark- 
able facility  of  decomposition.  It  is  a liquid  substance,  pos- 
sesses bleaching  powers,  and  is  heavier  than  water. 


LECTURE  XLIII. 

Nitrogen. — Preparation  of  Nitrogen. — Properties. — Its 
Indifferent  Nature. — Its  Oxygen  Compounds. — Atmos- 
pheric  Air. — Constitution  of. — Dimerisions  of — Re- 
lations to  Organization. — Density  and  Temperature. 
— Fixed  and  Variable  Constituents.  — Experimental 
Proofs  of  its  Pressure. 

NITROGEN.  iY=1419. 

Nitrogen  gas  is  most  readily  procured  from  the  atmos- 
pheric air  by  burning  phosphorus  in  a bell  jar  over  the  pneu- 
matic trough.  If  a piece  of  phosphorus  be  laid  in  a cup 

What  is  the  relation  of  water  to  acids,  bases,  and  salts  ? By  what  pro- 
cess is  water  purified  ? What  is  the  constitution  and  properties  of  the  deut- 
oxide of  hydrogen  ? What  is  the  process  for  preparing  nitrogen  by  phos- 
phorus ? 


198 


NITROGEN  GAS. 


(Fig.  184)  and  set  on  fire,  all  the 
oxygen  in  the  air  of  the  jar,  a, 
will  he  consumed,  white  flakes 
of  phosphoric  acid  forming,  and 
these  being  finally  dissolved  in 
the  water  of  the  trough,  d,  there 
is  left  behind  nitrogen,  contami- 
nated to  a small  extent  by  the 
vapor  of  phosphorus. 

If  nitrate  of  ammonia  be  placed 
in  a retort,  and  the  temperature 
raised  until  it  emits  protoxide  of  nitrogen,  and  at  that  mo- 
ment, by  means  of  a wire  passing  through  a cork  in  the  tub- 
ulure,  a piece  of  zinc  is  lowered  down  upon  the  melted  mass, 
oxide  of  zinc  is  produced,  and  nitrogen  gas  escapes.  The 
decomposition  is  very  simple, 

NO  . . Zn=i  Zn  O . . N. 

Nitrogen  gas  is  a colorless,  tasteless,  and  inodorous  body, 
very  sparingly  soluble  in  water,  that  liquid  dissolving  but 
1^  per  cent,  of  its  volume.  It  is  lighter  than  atmospheric 
air,  its  specific  gravity  being  0*976.  Its  atomic  weight  is 
14*19.  It  does  not  support  combustion  nor  respiration,  and 
from  the  latter  circumstance  obtained  formerly  the  name  of 
azote  ; but  it  does  not  exert  any  directly  poisonous  agency 
on  the  animal  system. 

Nitrogen  gas  is  little  disposed  to  unite  with  other  bodies, 
except  when  either  it  or  they  are  in  the  nascent  state.  Its 
compounds,  too,  are  prone  to  decompose  from  trivial  causes  ; 
hence  it  is  among  them  that  we  find  some  of  the  most  re- 
markably detonating  bodies.  Many  animal  and  vegetable 
substances,  into  the  composition  of  which  it  enters,  are 
characterized  by  the  facility  with  which  they  tend  to  un- 
dergo putrefactive  changes,  and,  as  we  shall  hereafter  find, 
ferments  owe  their  remarkable  powers  to  the  presence  of 
this  element. 

Nitrogen  unites  with  oxygen,  and  forms  five  different 
bodies, 

NO . ..NO^ . . . iVOg . ..NO^.. . NO,. 

Their  names  are 

How  may  it  be  made  from  nitrate  of  ammonia?  What  are  the  proper- 
ties of  this  gas  ? Why  does  it  give  rise  to  so  many  explosive  bodies  ? To 
what  is  the  property  of  ferments  due  ? How  many  compounds  of  oxygen 
and  nitrogen  are  there  1 


Fig.  184. 


THE  ATMOSPHERIC  AIR. 


199 


Protoxide  of  nitrogen.  Nitrous  acid. 

Deutoxide  of  nitrogen.  Nitric  acid. 

Hyponitrous  acid. 

With  oxygen,  also,  it  forms  atmospheric  air  ; hut  this  is  a 
mixture,  and  not  a compound. 

ATMOSPHERIC  AIR. 

The  mechanical  properties  and  constitution  of  the  atmos- 
phere are  so  important,  that  I shall  here  introduce  the  con- 
sideration of  them  before  passing  to  the  description  of  the 
oxides  of  nitrogen. 

The  atmosphere  consists  chiefly  of  oxygen  and  nitrogen 
gases,  in  the  proportion  of  about  21  volumes  of  the  former 
to  79  of  the  latter.  It  also  contains  a minute  but  essential 
quantity  of  carbonic  acid,  which,  however,  varies  at  differ- 
ent times,  10,000  parts  of  air  containing,  on  an  average, 
about  five  parts  of  this  gas.  Besides  these,  there  are  found 
in  it  variable  quantities  of  the  vapor  of  water,  and  traces 
of  ammonia,  sulphureted  hydrogen,  and  carbureted  hydro- 
gen. It  is  a colorless,  invisible,  elastic  substance,  815  times 
lighter  than  water,  and  is  taken  as  the  standard  of  compar- 
ison for  the  specific  gravity  of  gases.  Its  specific  gravity  is, 
therefore,  =1  000.  One  hundred  cubic  inches  of  it  weigh, 
at  the  mean  temperature  and  pressure,  very  nearly  31  grs. 

There  are  many  methods  by  which  the  analysis  of  the 
air  can  be  effected.  Ure’s  eudiom- 
eter, Fig.  185,  which  consists  of  a 
siphon  tube,  closed  at  one  end  and 
open  at  the  other,  may  be  used  for 
this  purpose.  Into  the  closed  branch 
of  the  instrument,  which  is  also  grad- 
uated, a measured  quantity  of  air  is 
introduced,  and  to  it  is  added  an 
equal  volume  of  hydrogen.  The 
bend  of  the  tube  is  occupied  by  wa- 
ter, as  shown  in  the  figure,  a column 
of  air  intervening  between  this  water  and  the  open  extrem- 
ity of  the  tube.  On  this  the  thumb  is  closely  pressed,  a§ 
represented,  and  an  electric  spark  passed  through  the  in- 
strument by  the  aid  of  its  platina  wires.  This  sets  the 
gases  on  fire  ; the  column  of  air  beneath  the  thumb  acting 

Of  what  is  the  atmospheric  air  composed  ? What  is  its  specific  gravity  ? 
What  is  the  weight  of  100  cubic  inches  of  it  ? How  may  it  be  analysed 
by  Ure’s  eudiometer  ? ‘ 


Fig.  185. 


200 


ANALYSIS  OF  Till:  AIR. 


Fig.  186. 


like  a spring  to  repress  the  movement  at  the  time  of  the 
explosion.  The  amount  of  gas  then  left  is  ascertained  on 
the  divisions,  and  one  third  of  the  deficit  represents  the 
quantity  of  oxygen  originally  present. 

To  enable  the  experimenter  to  operate  on  larger  quanti- 
ties of  gas,  Brunner’s  instrument  may  be  used.  It  consists 
of  a tube,  ah  with  three  bulbs  blown 
upon  it ; these  bulbs  are  filled  with  cot- 
ton which  has  been  impregnated  with 
melted  phosphorus.  The  tube  is  attach- 
ed, by  means  of  a cork,  to  a glass  vessel, 
filled  with  mercury.  On  opening  the 
stop-cock,  e,  the  mercury  flows  out,  at- 
mospheric air  introducing  itself  by  a ^ c, 
and  its  oxygen  being  removed  by  means 
of  the  extensive  surface  of  phosphorus 
which  the  cotton  presents.  Consequent- 
ly, by  measuring  the  mercury  which  has 
flowed  out,  we  ascertain  the  quantity  of 
nitrogen  introduced  into  the  vessel  and 
the  increased  weight  of  the  tube  a h c determines  the 
amount  of  oxygen. 

The  result  of  such  experiments  shows  that  the  atmos- 
pheric air  is  composed  of  from  20*79  to  21*08  parts  of  oxy- 
gen in  100  volumes.  By  weight,  its  constitution  is  about, 


Oxygen  . 
Nitrogen  . 


23*04 

76-9G 

100*00 


The  earth’s  atmosphere  does  not  extend  indefinitely  into 
space,  but  terminates  at  an  altitude  of  about  fifty  miles.  It 
forms,  therefore,  a mere  film  on  the  face  of  the  earth,  for 
the  diameter  of  the  globe  is  nearly  8000  miles.  If  a rep- 
resentation of  it  were  placed  on  a common  twelve-inch 
globe,  it  would  scarcely  be  one  eighth  of  an  inch  thick. 

Its  relations  to  the  world  of  organization,  are  full  of  in- 
terest. All  plants  come  from  it,  and  all  animals  return  to 
it,  so  that  it  stands  as  the  bond  of  connection  between  these 
orders  of  life. 

As  we  ascend  to  more  elevated  regions  the  air  becomes 
less  dense,  for  the  obvious  reason  that,  as  it  is  a very  com- 


How  may  atmospheric  air  be  analyzed  by  Brunner’s  instrument  ? What 
is  its  constitution  by  volume  and  by  weight  ? To  what  distance  does  it  ex- 
tend ? What  are  its  relations  to  animals  and  plants  ? 


DENSITY  OF  THE  AIR. 


201 


pressible  body,  those  portions  of  it  nearest  the  ground  have 
to  sustain  the  weight  of  the  superincumbent  mass,  and  are 
therefore  more  dense  ; but  in  the  higher  regions,  where  the 
superincumbent  pressure  is  less,  the  air  is  more  rare,  as  is 
shown  in  the  following  table  : 


Heij^ht  in  Miles. 

Voluma  of  Air. 

Barometric  Inches. 

O' 

1 

30- 

2-705 

2 

15- 

5.41 

4 

7-5 

8-115 

8 

3-75 

10-82 

16 

1-875 

13-525 

32 

-9375 

16.23 

64 

'46875 

which  also  shows  that  the  great  mass  of  the  atmosphere  is 
comprehended  within  a very  short  distance  of  the  earth’s 
surface.  At  different  altitudes  it  is  of  very  different  tem- 
peratures, being  colder  as  the  altitude  is  greater. 

Of  the  constituents  of  the  air,  the  oxygen  and  nitrogen 
are  usually  spoken  of  as  fixed,  the  carbonic  acid,  ammonia, 
and  water  as  variable.  There  are  causes  in  operation  which 
tend  continually  to  impress  changes  in  the  amount  of  all 
these  bodies.  Every  process  of  combustion,  and  the  respi- 
ration of  every  animal,  remove  oxygen  and  replace  it  by  car- 
bonic acid.  But  the  growth  of  plants  has  the  reverse  ac- 
tion, removing  carbonic  acid  and  replacing  it  by  oxygen,  so 
that  for  many  centuries  in  succession  the  constitution  of  the 
atmosphere  is  unchanged. 

Of  the  mechanical  properties  of  the  air,  the  first  to  which 
we  have  to  direct  our  attention  is  its  pressure,  Avhich  Fi^.i87. 
takes  effect  equally  in  all  directions,  upward,  down- 
ward, and  laterally.  Thus,  if  we  take  a glass  tube 
several  feet  long,  a,  Fig,  187,  closed  at  one  end  and 
open  at  the  other,  and  having  filled  it  full  of  water, 

Ft  188  mouth  of  it  a piece  of  card, 

b,  and  turn  it  upside  down,  the  card  will 
not  fall  off,  nor  the  water  flow  out ; they 
||l  remain,  as  it  were,  suspended  on  nothing, 

/IIm  reality  sustained  by  the  upward  pressure  of 

I I the  air.  Or  if  we  take  a bottle,  a,  Fig,  188,  with 
llIP^  a hole,  5,  half  an  inch  in  diameter,  in  the  bottom  of 

h it,  and  having  filled  it  with  water,  close  the  mouth 

Why  does  its  density  decrease  with  the  altitude  ? How  does  its  tem- 
perature vary  ? Wliich  are  the  fixed,  and  which  the  variable  constituents 
©f  the  air  ^ Give  some  illustrations  of  the  upward  pressure  of  the  air. 

I 2 


202 


PRESSURE  OF  THE  AIR. 


Fig.  189. 


of  it  with  the  finger,  it  may  be  held  up  in  the  air  without 
the  water  flowing  out,  although  the  aperture  h is  wide  open. 
In  this  instance,  again,  it  is  the  upward  pressure  of  the  air 
which  sustains  the  liquid. 

Let  the  glass  globe  a,  Fig,  189,  with  its  neck 
h,  be  inverted  in  some  water  contained  in  ajar, 
c,  and  the  whole  covered  by  an  air-pump  re- 
ceiver. As  the  receiver  is  exhausted,  bubbles  of 
air  pass  through  the  water  and  escape  away,  but 
as  soon  as  the  pressure  is  restored,  the  water  is 
forced  out  of  the  jar  upward  into  the  globe. 

The  air-pump  enables  us  to  exhibit  in  a very 
striking  manner  many  of  the  chief  mechanical  properties 
of  the  atmosphere.  Thus,  if  upon  the  plate  of  it  there  be 
190.  placed  a glass  receiver,  a.  Fig.  190,  as  soon  as 
the  air  is  exhausted  from  its  interior,  the  superin- 
cumbent pressure  retains  the  glass  so  firmly  in  con- 
tact  that  it  is  impossible  to  lilt  it  off,  but  as  soon 
as  the  air  is  readmitted,  it  can  be  easily  removed. 
If  within  the  receiver  a a smaller  one,  h,  be  placed, 
and  exhaustion  made,  while  a is  fixed,  h can  be 
easily  moved  by  shaking  the  pump,  but  on  letting  in  the  air,  a 
becomes  loose  and  h firmly  pressed  in  contact  with  the  plate. 


Fig.  191. 


If  over  the  mouth  of  a 
j ar.  Fig.  191,  placed  upon 
the  pump,  the  palm  of  the 
hand  be  laid,  as  the  air  is 
exhausted  it  is  pressed  in 
close  contact  with  the  jar, 
and  can  only  be  removed 
by  the  exertion  of  a very 

considerable  force. 

On  a small  plate,  a.  Fig.  192,  furnished 
with  a stop-cock,  h,  terminating  in  a fine  jet,  c, 
let  there  be  placed  a tall  glass  receiver.  The 
stop-cock  being  now  screwed  into  the  pump 
and  opened,  the  air  may  be  exhausted  from  the 
interior  of  the  receiver  and  the  stop-cock  closed. 
But  being  now  opened  under  the  surface  of 
some  water  in  a cup,  the  water  passes  through 
the  jet  and  rises  to  the  top  of  the  jar,  forming 
a fountain  in  vacuo. 


Give  an  illustration  of  its  downward  pressure.  Describe  the  experiment 
represented  in  Fiir.  1 91.  Describe  the  fountain  in  vacuo. 


PRESSURE  OF  THE  AIR. 


203 


LECTURE  XLIV. 

« 

Atmospheric  Aifw. — Pressure  of  the  Air. — Simple  Means 
of  Exhaustion. — Determination  of  theW eight  of  Air. — 
Amount  of  Pressure. — Elasticity  of  Air . — Exists  in  the 
Pores  of  Bodies. — Respiration  of  Fishes. — Measure  of 
Elastic  Force. 


The  Magdeburg  hemispheres,  invented  by  Otto  Guericke, 
who  also  invented  the  air  pump,  illustrate  in  a very  striking 
manner  atmospheric  pressure.  They  consist  of  a Fig.  193. 
pair  of  brass  hemispheres,  a Fig.  193,  with 
handles ; they  fit,  without  leakage,  to  each  other 
by  a flange,  so  as  to  form  a perfect  sphere.  One 
of  them  has  a stop-cock,  through  which  the  air 
may  be  exhausted,  and  on  this  being  done,  it  will 
be  found  almost  impossible  to  pull  them  apart, 
though  as  soon  as  the  air  is  readmitted,  and  its 
pressure  restored  to  the  interior,  they  will  fall  asunder  by 
their  own  weight. 

If  over  the  mouth  of  an  open  receiver,  a,  Fig.  194,  a piece 
of  bladder  be  tightly  tied  with  a waxed  thread.  Fig.  194. 
when  the  air  is  exhausted  the  bladder  becomes 
deeply  depressed  into  a spherical  concavity  by 
the  superincumbent  pressure,  and  finally  bursts 
inward  with  a loud  explosion. 

It  is  upon  the  principle  of  atmospheric  pressure 
that  the  various  instruments  used  by  surgeons  for  cupping 
act.  One  of  the  most  simple  methods  of  performing  this 
operation  is  to  place  the  cupping  glass  for  a moment  over 
the  flame  of  a spirit  lamp,  and  then  transfer  it  rapidly  to 
the  skin.  Spirits  of  wine,  when  burning,  forms  a very  large 
quantity  of  steam,  which  of  course  fills  the  interior  of  the 
glass  in  a rarefied  state  by  reason  of  the  high  temperature 
of  the  flame.  As  soon  as  this  steam  condenses  a vacuum  is 
formed,  and  the  soft  surface  on  which  the  cup  is  placed  is 
pressed  into  its  interior. 

For  many  of  these  experiments  an  air  pump  is  not  nec- 

What  are  the  Magdeburg  hemispheres  ? What  is  the  principle  illustrated 
in  these  various  experiments  ? How  is  the  process  of  cupping  performed  ? 


204 


WEIGHT  OF  AIR. 


essarily  required,  but  simple  contrivances  will  answer  in  its 
Fig.  195.  stead.  Thus,  if  we  take  an  eight-ounce  vial, 
«,  Fig.  195,  and  fit  to  the  mouth  of  it  a cork, 
bi  through  which  there  passes  a piece  of  glass 
tube,  c,  drawn  into  a narrow  jet  at  one  ex- 
i J tremity,  but  open  at  the  other,  by  placing 
finger  over  the  opening  and  introducing 
it  into  the  mouth,  the  air,  by  the  action  of 
the  tongue  and  the  muscles  of  the  mouth,  may  be  sucked 
out  to  a great  extent ; and  when  the  exhaustion  has  .been 
carried,  by  this  means,  as  far  as  possible,  by  pressing  the 
finger  over  the  opening,  it  will  close  it,  acting,  therefore, 
as  a valve.  And  now,  if  the  bottle  be  turned  upside  down, 
as  at  e,  the  tube  dipping  beneath  some  water  in  a cup,  as 
Fig.  196.  soon  as  the  finger  is  removed  the 

water  is  pressed  upward,  and 
forms  a fountain  in  vacuo. 

The  pressure  of  the  air  depends 
primarily  on  the  fact  that  it  is  a 
heavy  body,  as  may  be  proved  by 
the  direct  experiment  of  weighing 
it.  For  this  purpose,  let  a light 
glass  flask,  a,  Fig.  196,  fitted 
with  a stop-cock,  be  counterpoised 
at  the  balance  • then  let  the  air 
be  exhausted  from  it,  and  its 
weight  determined  again.  It  will 
now  be  found  lighter  than  before ; 
but  upon  opening  the  stop-cock  it 
will  regain  its  original  weight. 
Experiments  made  in  this  man- 
ner show  that  a flask  containing 
100  cubic  inches  will,  when  ex- 
hausted, weigh  about  thirty-one 
grains  less,  and  therefore  we  infer  that  that  is  the  weight 
of  100  cubic  inches  of  atmospheric  air. 

Atmospheric  air  is  used  as  the  standard  of  comparison  of 
the  specific  gravities  of  other  gaseous  bodies.  The  process 
for  the  determination  is  very  simple.  A glass  globe,  g.  Fig. 
197,  holding  20  or  30  cubic  inches,  is  exhausted  of  air, 

Describe  a simple  method  by  which  partial  exhaustion  may  be  produced 
by  the  mouth.  How  may  the  weight  of  air  be  directly  ascertained  ? In 
what  manner  may  the  relative  weight  of  other  gases  be  determined  ? 


SPECIFIC  GRAVITY  OF  GASES. 


205 


Fig.  197. 


and  by  means  of  the  stop-cocks,  e d,  attached  to  the  jar,  c, 
containing  the  gas  to  be  tried.  This  gas,  which  is  con- 
fined by  mercury,  has  been  pass- 
ed through  the  drying  tube,  a, 
by  the  delivering  tube,  5,  into 
the  jar,  which  should  be  grad- 
uated. On  opening  the  cocks, 
e d,  the  gas  flows  into  the  ex- 
hausted globe  ; the  quantity  in- 
troduced may  be  determined  on 
the  graduation,  and  its  weight 
ascertained  by  the  balance. 

There  are  several  dilTerent 
methods  of  stating  the  amount , 
of  the  mean  pressure  of  the  air  ; 
thus  we  say  that  it  is  equal  to  15  pounds  on  the  square 
inch,  or  to  a column  of  mercury  30  inches  long,  or  to  a col- 
umn of  water  30  feet  long. 

That  air  is  a highly  elastic  substance  can  be  readily 
Fig.  198.  shown.  Under  a receiver  {Fig.  198)  let  there  be 
placed  a half-blown  bladder,  the  neck  of  which  is 
tightly  tied ; as  the  air  is  removed  from  the  re- 
ceiver the  bladder  distends,  but  on 
restoring  the  pressure  it  becomes 
as  flaccid  as  it  was  before,  showing 
’ that  the  air  included  in  it  expands 
and  contracts  as  the  pressure  upon  it  is  made 
to  vary. 

This  may  be  still  better  shown  by  taking 
a . small  India-rubber  bag  {Fig.  199),  the 
mouth  of  which  is  closed  tightly,  and  using 
it  instead  of  the  bladder  in  the  last  experi- 
ment. On  rarefying  the  air  in  the  receiver,  the 
bag  begins  to  dilate,  and  may  be  extended  to 
several  times  its  original  dimensions,  as  shown 
in  the  dotted  line  ; but  as  soon  ,as  the  pressure 
is  restored,  it  returns  to  its  original  size. 

Nor  does  this  expansion  take  place  with  an 
inconsiderable  force.  If  a flaccid  bladder  be 
placed,  as  in  Fig.  200,  with  several  heavy  lead- 

What  is  the  pressure  of  the  air  on  a square  inch  equal  to  ? What  is  nearly 
the  equivalent  length  of  a mercurial  and  water  column  ? How  may  the 
elasticity  of  air  be  illustrated  ? How  may  it  be  shown  by  an  India-rubber 
bas  ? Give  an  illustration  of  the  amount  of  this  force. 


Fig.  199. 


206 


ELASTICITY  OP  AIR. 


en  weights  put  upon  it,  as  soon  as  it  is  caused  to  dilate  by 
removing  the  pressure,  it  will  push  up  the  weights.  Nor 
does  it  lose  its  elastic  force  or  spring  by  being  long  pent  up 
in  close  vessels.  Some  of  the  old  chemists  kept  air  com- 
pressed in  copper  globes  for  months,  and  found  that,  as  soon 
as  an  opening  was  made  for  it,  it  expanded  to  its  original 
dimensions. 

Let  there  be  taken  a glass  bulb,  a {Fig.  201),  the  open 
neck  of  which,  h,  dips  beneath  some  water  in  a 
j ar,  c,  and  let  the  bulb  and  tube  be  full  of  water, 
with  the  exception  of  a small  space  occupied  by 
atmospheric  air.  On  covering  the  apparatus  with 
an  air-pump  receiver,  dy  and  exhausting,  the  bub- 
ble of  air,  a,  gradually  expands,  and  after  a time, 
as  the  action  of  the  machine  is  continued,  fills 
the  entire  glass,  both  bulb  and  tube ; but  as  the 
pressure  is  restored,  it  contracts  again,  and  goes  back  to  its 
original  size. 

By  taking  advantage  of  the  expansibility  of  air  under  re- 
Fig.  202.  duction  of  pressure,  we  are  able  to  demon-  203. 
strate  its  existence  in  the  pores  of  many  bod- 
ies ; thus,  if  we  place  in  glasses  of  water  an 
egg  {Fig.  202),  an  apple  {Fig.  203),  or  other 
such  objects,  and,  covering  them  with  a re- 
ceiver, exhaust,  we  shall  see  innumerable 
bubbles  of  air  escaping  through  the  water. 

The  same  observation  may  be  made  in  the 
case  of  many  liquids  which  hold  gaseous  sub- 
stances dissolved.  A glass  of  ale  placed  in 
an  exhausted  receiver  {Fig.  204)  foams  from  the  escape 

Fig.  204.  carbonic  acid  gas,  and  even  clear  spring  or  river 
water,  examined  in  the  same  manner  oo5. 
{Fig.  205),  is  found  to  contain  a large 
quantity  of  air  in  solution. 

This  last  fact  is  of  considerable  im- 
portance, for  it  is  by  the  aid  of  this  air 
that  the  respiratory  function  of  fishes 
is  carried  forward.  On  examination, 
however,  it  is  found  that  this  is  not 
true  atmospheric  air,  but  a mixture,  which  is 

How  may  the  presence  of  air  be  detected  in  the  pores  of  solid  bodies  ? 
How  may  air  be  shown  to  exist  dissolved  in  liquids  ? Of  w'hat  use  is  the 
air  dissolved  in  water? 


Fig.  201. 


RESPIRATION  OF  FISHES. 


207 


richer  in  oxygen.  The  atmosphere  con-  Fig.  206. 

tains  21  per  cent,  of  oxygen,  but  this  gas  - 
contains  33 . The  cause  of  the  difference 
is  the  unequal  solubility  of  oxygen  and 
nitrogen ; for  the  former  gas  being  much 
the  more  soluble,  the  water  takes  up  rel- 
atively a greater  portion  of  it  from  the 
air.  Fishes,  therefore,  respire  this  gas, 
its  richness  in  oxygen  making  up  for  its 
inferior  amount  ; and  when  they  are 
placed  in  water  which  has  been  in  an 
exhausted  receiver,  they  die.  Their 
movements,  also,  are,  to  a certain  ex- 
tent, regulated  by  the  air  contained  in  a receptacle,  or  blad- 
der, in  their  bodies ; by  the  compression  of  it  they  can  de- 
scend, and  by  its  expansion  rise.  If  they  be  placed  in  water 
in  a partially  exhausted  receiver,  they  float  on  the  surface, 
or  can  only  descend  to  the  bottom  for  a moment  by  violent 
muscular  exertion. 

The  necessity  of  air  to  the  support  of  combustion  may  be 
illustrated  by  comparing  the  length  of  time  a candle  will 
burn  in  a large  receiver  full  of  air,  and  in  the  same  exhaust- 
ed. In  the  latter  case  it  speedily  dies  out,  the  smoke  de- 
scending to  the  bottom  of  the  jar  in  the  rarefied  medium 
around. 

Substances  prone  to  decay,  such  as  meats  and  fruits,  may 
be  preserved  for  a length  of  time  Fig.  207. 

in  vessels  void  of  air.  The  pro- 
cess is  illustrated  in  Fig.  207. 

The  fruits  are  placed  in  a large 
jar  closed  by  a sound  cork,  cov- 
ered with  sealing-wax.  A small 
hole  is  made  through  the  cork, 
and  the  jar  covered  by  an  air- 
pump  receiver.  On  exhausting, 
the  air  passes  out  through  the 
hole,  and  when  the  vacuum  is  per- 
fect, the  hole  is  closed  by  melting 
the  wax  by  the  sunbeams  con  verg- 
ed by  a convex  lens,  the  access  of  the  air  being  thus  cut  ofl. 

What  is  its  composition  How  may  the  necessity  of  air  to  the  support 
of  combustion  be  proved?  By  what  means  may  objects  be  preserved  from 
its  influence? 


208 


THE  BAROMETER. 


From  the  foregoing  experiments  and  considerations,  it  ap- 
pears that  the  primary  fact  in  pneumatics  is,  that  the  air 
has  weight  ; from  this,  by  a necessary  consequence,  arises 
its  pressure  and  the  inequality  of  density  of  the  atmosphere 
at  different  altitudes.  It  also  follows  that  the  elastic  force 
of  the  air  must  be  precisely  equal  to  the  pressure  upon  it. 
In  any  given  stratum  of  air,  as,  for  instance,  that  which 
rests  upon  the  surface  of  the  earth,  the  pressure  of  the  su- 
perincumbent mass  is  equipoised  by  the  elastic  force  ; if  the 
elastic  force  were  less,  compression  would  ensue  ; if  great- 
er, dilatation.  The  pressure  and  the  elastic  force  must, 
therefore,  be  equal  to  each  other. 


LECTURE  XLV. 

Atmospheric  Air. — The  Barometer . — Description  of  it. — 
Cause  of  the  Phenomenon. — Proof  that  it  is  the  Press- 
ure of  the  Air. — History  of  the  Invention. — PaschaVs 
Experiment. — Illustrations  of  the  Nature. of  Pressure. 
— Variability  of  Pressure. — Point  of  Perpetual  Con- 
gelation.— Local  Disturbances  in  the  Constitution  of 
the  Air  .—Diffusion  of  Gases. — The  Air  is  a Mixture. 
— Marriotte's  Law.  — Gay-Lussac' s and  Rudberg's 
Laio. 

If  we  take  a tube  of  glass,  a b.  Fig.  208,  more  than 
thirty  inches  long,  closed  at  one  end  and  open  at  the  other 
Fig.  208.  end,  and,  having  filled  it  with  quicksilver.  Fig.  209. 
invert  it  in  a cup,  c,  filled  with  that  metal, 

’ the  mercury  will  not  flow  out  of  the  tube, 
but  will  remain  suspended  at  a height 
of  twenty-eight  or  thirty  inches.  If  there 
be  placed  beside  the  tube  a scale,  d,  divided 
into  inches  and  decimal  parts,  the  zero  of 
the  division  coinciding  with  the  level  of  the 
mercury  in  the  cup,  such  an  instrument 
^ forms  the  barometer. 

The  cause  of  the  suspension  of  the  mer- 
cury in  the  tube  is  the  pressure  of  the  air.  This 
may  be  demonstrated  by  placing  over  the  barome- 

Whatis  the  relation  between  the  pressure  and  the  elastic  force  of  the  air  ? 
Describe  the  barometer.  What  is  it  which  supports  the  mercurial  column  ? 


PRINCIPLE  OF  THE  BAROMETER. 


209 


ter  a tall  air-pump  receiver,  and  exhausting.  It  will  be 
found  that,  as  the  pressure  in  the  interior  of  the  receiver 
is  reduced,  the  column  of  mercury  in  the  barometer  falls, 
and  on  restoring  the  pressure,  it  rises  to  its  original  point. 

The  same  fact  may  be  proved  in  another  manner,  210. 
If  a tube,  upward  of  thirty  inches  long,  the  upper 
extremity  of  which  is  closed  by  a piece  of  bladder, 
be  filled  with  mercury  and  inverted  in  a cup,  as 
shown  in  Fig.  210,  the  bladder  will  be  found  deep- 
ly depressed,  the  pressure  of  the  air  in  that  direc- 
tion being  borne  by  it ; but  if  now  a minute  pinhole 
is  made  in  the  bladder,  so  as  to  allow  the  air  to 
press  upon  the  top  of  the  mercury,  the  column  rap- 
idly descends,  flowing  out  of  the  tube. 

The  barometer  was  originally  invented  by  Torricelli. 
Some  plumbers,  working  for  the  Duke  of  Florence,  found 
that  it  was  impossible  to  make  a pump  which  should  raise 
water  more  than  about  thirty  feet.  This  fact  eventually 
coming  to  the  knowledge  of  Torricelli,  he  suspected  that  the 
water  rose  in  those  machines  in  consequence  of  the  press- 
ure of  the  air,  and  not  through  Nature’s  abhorrence  of  a vac- 
uum, as  was  at  that  time  supposed.  But  if  the  limit  to 
which  water  can  be  raised  by  a pump  is  reached  when  the 
pressure  of  the  column  of  liquid  equilibrates  the  pressure  of 
the  air,  it  follows  that  if  a heavier  fluid  than  water  be  used, 
the  height  to  which  it  can  be  raised  is  less.  A pump  ought, 
therefore,  to  lift  quicksilver  only  about  as  many  inches  as 
it  can  lift  water  feet  ; for  the  weight  of  these  liquids  is 
about  as  one  to  thirteen  and  a half ; and,  accordingly,  Torri- 
celli found,  by  means  of  a small  pump  fixed  to  a long  glass 
tube,  that  such,  in  reality,  is  the  case.  The  barometer  is  a 
simplification  of  the  same  apparatus. 

That  it  is  the  pressure  of  the  air  which  sustains  the  mer- 
curial column  was  satisfactorily  proved  by  Paschal,  who 
reasoned  that,  if  this  were  the  case,  the  barometric  column 
ought  to  be  shorter  on  the  top  of  a mountain  than  in  a val- 
ley, because  in  the  former  position  that  pressure  must  neces- 
sarily be  less.  On  the  experiment  being  made,  his  reason- 
ing was  found  to  be  true. 

The  principle  of  the  barometer  may  be  illustrated  by  sub- 

How  may  this  be  proved  ? By  whom  w^as  the  barometer  invented  ? 
What  were  the  circumstances  of  the  invention?  What  was  Paschal’s  ex- 
periment ? What  did  k prove  ? 


210 


TEMPERATURE  OF  THE  ATMOSPHERE. 


stituting  for  the  pressure  of  air  the  pressure  of  a column  of 
211  Thus,  if  we  pour  some  quicksilver  into  the 

’ bottom  of  a deep  glass  jar,  a,  Fig,  211,  and  plunge 
Jc  into  it  3*  tube,  b,  open  at  both  ends,  the  quick- 

I I silver  will  rise  in  this  tube,  so  that  its  level  on  the 
J|  inside  will  be  coincident  with  that  on  the  outside. 
I But  if  now  we  begin  to  fill  the  jar  with  water,  c, 

I I for  every  thirteen  and  a half  inches  in  depth  poured 
I quicksilver,  will  rise  one  inch,  the  mer- 

jyiJ[  curial  column  counterpoising  the  column  of  water. 

And,  on  the  same  principle,  the  column  of  quicksil- 
ver in  the  barometer  counterpoises  that  of  the  air  to  the  top 
of  the  atmosphere. 

Mr.  Boyle  discovered  that  the  pressure  of  the  air  is  not 
always  the  same,  but  it  undergoes  many  variations,  the  mer- 
curial column  sometimes  falling  near  to  27  inches,  or  rising 
above  30.  Jhe  range  is  commonly  estimated  at  2*5  inches. 
It  is  considerably  less  in  the  tropics.  These  changes  of  press- 
ure are  exceedingly  irregular,  and  are  connected  with  meteor- 
ological phenomena.  There  are  also  diurnal  variations,  the 
column  rising  twice  in  the  twenty-four  hours.  In  winter 
the  first  maximum  is  about  nine  A.M.,  and  the  minimum  at 
three  P.M.,  the  second  maximum  being  about  nine  P.M. 

It  has  already  been  observed  that  the  mean  pressure  of 
the  air  is  estimated  at  15  pounds  upon  a square  inch,  or 
equal  to  a column  30  inches  long.  A man  of  average  size 
sustains  a pressure  on  the  surface  of  his  body  of  nearly 
thirty  thousand  pounds. 

The  temperature  of  the  atmosphere  is  lower  as  we  ascend 
to  more  elevated  regions.  A point,  therefore,  can  always 
be  reached  over  any  place  of  which  the  temperature  never 
rises  over  32^  F.,  and  where  water  is  always  frozen.  This 
point  is  known  under  the  name  of  the  point  of  perpetual 
congelation.  Its  altitude  differs  very  much  in  different 
places,  being  highest  at  the  equator,  and  lower  as  we  go 
toward  the  poles.  It  is  at 


How  may  the  phenomena  of  the  barometer  be  illustrated  by  the  pressure 
of  a water  column  ? What  is  the  extent  of  the  irregular  variations  of  press- 
ure ? What  are  the  diurnal  variations  ? At  what  times  do  the  maxima  and 
minima  occur?  What  is  the  point  of  perpetual  congelation?  How  does 
it  vary  with  the  latitude  ? 


The  Equator  . . 

Latitude  40°  . . 


15,000  feet. 
Q non  “ 


“ 85°  . 


DIFFUSION  OF  GASES. 


211 


Many  causes  conspire  to  give  rise  to  local  disturbances  in 
the  constitution  of  the  air.  In  its  lower  strata  combustion 
and  respiration  are  actively  going  on ; they  tend  to  dimin- 
ish the  oxygen  and  increase  the  carbonic  acid.  At  the 
equator  the  etlect  of  a constantly  brilliant  sunshine  on  the 
leaves  of  plants  is  to  diminish  the  carbonic  acid  and  in- 
crease the  oxygen.  But  notwithstanding  these  local  disturb- 
ances, and  also  the  fact  that  the  constituents  of  the  Fig.  212. 
air  are  of  very  different  specific  gravities,  the  con- 
stitution of  the  atmosphere  is  nearly  the  same  in  all 
places.  This  commixture  is  partly  effected  by  the 
mechanical  action  of  winds,  and  partly  by  the  prop- 
erty which  gases  have  of  diffusing  into  each  other. 

Thus,  if  two  vials,  a and  e,  Fig.  212,  communi- 
cate with  each  other  by  means  of  stop-cocks,  h c cl^ 
and  if,  in  a,  a light  gas,  such  as  hydrogen,  is  placed, 
and  in  e a heavy  gas,  as  carbonic  acid,  in  a few 
minutes  after  the  stop-cocks  are  opened  the  gases 
will  diffuse  into  each  other,  the  light  one  descend- 
ing and  the  heavy  one  ascending,  until  they  are 
perfectly  commixed.  And  this  effect  will  take 
place  even  though  a barrier  should  intervene.  Thus  Dr. 
Mitchell  found  that  gases  would  readily  pass  through  the 
close  texture  of  India-rubber  to  mingle  with  each  013. 
other  ; and  I have  observed  the  same  in  the  case  of 
films  of  water.  Thus,  if  a bottle,  a.  Fig.  213,  full 
of  atmospheric  air,  have  its  mouth  closed  by  a film 
of  soap-water  spread  over  it  by  the  finger,  and  then 
be  placed  under  a bell  jar  containing  protoxide  of 
nitrogen,  this  latter  gas  passes  rapidly  through  the 
film,  and  distends  it  into  a bubble  by  forcing  its  way  into 
the  bottle.  The  force  with  which  gases  will  thus  pass  into 
each  other  is  sometimes  very  great.  I have  proved  that  sul- 
phureted  hydrogen  will  difiuse  into  atmospheric  air,  though 
resisted  by  a pressure  of  more  than  fifty  atmospheres. 

That  the  atmospheric  air  is  a mixture,  and  not  a com- 
pound, is  proved  by  its  easy  decomposibility,  its  refractive 
power,  and  by  the  fact  that  its  constituents  retain  their  prop- 
erties unchanged.  The  amount  of  its  oxygen  rnay  be  de- 

What  are  the  causes  which  tend  to  change  the  composition  of  the  air? 
What  is  meant  by  the  diffusion  of  gases  ? Does  this  take  place  through 
intervening  barriers  ? How  is  this  connected  with  the  constitution  of  the 
air?  What  proofs  are  there  that  the  atmosphere  is  a mixture,  and  not  a 
compound  ? 


212 


marriotte’s  law. 


termined  by  the  combustion  of  phosphorus,  or  detonation 
with  hydrogen  ; the  amount  of  its  carbonic  acid,  which  va- 
ries in  damp  or  dry  seasons,  being  dissolved  out  by  showers 
of  rain,  may  be  determined  by  potash  or  lime-water,  and  its 
aqueous  vapor  by  the  process  for  the  dew-point  already  de- 
scribed. 

Atmospheric  air  being  thus  an  elastic  and  compressible 
body,  it  remains  to  explain  the  law  which  determines 

Id  its  volume  under  changes  of  pressure.  This  is  known 
under  the  name  of  the  law  of  Marriotte,  and,  apply- 
ing to  many  other  gases  besides  atmospheric  air,  is 
to  the  effect  that  the  volume  of  a gas  is  inversely  as 
the  •pressure  upon  it.  This  law  is  of  the  utmost  im- 
portance in  gaseous  chemistry.  It  may  be  illustra- 
gb  ted  by  the  instrument  {Fig.  214),  where  a b is  d.  bent 
I tlrf  tube,  open  at  the  end  a,  and  closed  at  b.  The  branch 
w a may  be  several  feet  long,  and  b six  inches.  A 
small  quantity  of  mercury  is  poured  into  the  tube,  so  as  to 
occupy  the  bend  and  shut  up  a column  of  air  between  d 
and  b.  Now,  if  the  tube  is  filled  with  quicksilver  to  the 
height  of  30  inches,  as  to  a,  the  pressure  of  this  column  is 
exerted  on  the  air  in  the  closed  branch,  b;  and  as  there  are 
now  the  weight  of  two  atmospheres,  that  of  the  ordinary 
atmosphere  and  that  of  the  mercurial  column,  it  is  com- 
pressed into  half  its  former  volume,  c.  If  we  bring  upon  it 
three  atmospheres,  it  will  be  compressed  into  one  third ; if 
four,  to  one  fourth,  &c.  And  the  law  holds  good,  also,  for 
diminutions  of  pressure.  If,  on  a given  volume  of  gas,  the 
pressure  is  reduced  to  one  half,  the  volume  doubles  ; if  to 
one  third,  it  triples;  to  one  fourth,  it  quadruples ; in  all  cases 
the  volume  being  inversely  as  the  pressure. 

The  exact  amount  of  dilatation  of  atmospheric  air  for  ele- 
vations of  temperature  was  determined  by  Gay-Lussac  as  fol- 
lows : In  a tin  box,  A {Fig.  215),  containing  water,  there  is  in- 
troduced through  a perforation  at  d a bulb,  g,  with  a tube, 
g\  containing  the  air,  the  dilatation  of  which  is  to  be  meas- 
ured. This  air  has  been  previously  introduced  in  a state 
of  dryness  by  the  chloride  of  calcium  tube,  h K.  At  m is 
a globule  of  mercury,  which  acts  as  an  index,  and  confines 
the  air.  On  the  opposite  side  of  the  tin  box,  at  o,  a ther- 
mometer, S t bf\s  introduced,  and  another  one,  v,  passing 


What  is  Marriotte’s  law  ? How  may  its  truth  be  proved?  Give  exam 
pies  of  Marriotte’s  law.  What  is  the  law  of  Gay-Lussac  ? 


DILATATION  OF  ATMOSPHERIC  AIR. 


213 


through  the  top  of  the  box,  occupies  the  center.  The  box 
is  first  filled  with  water  containing  fragments  of  ice,  and 
when  the  thermometers  are  at  32^,  the  position  of  the  index, 
is  marked.  The  furnace  is  then  lighted,  and  when  the 
water  boils,  and  the  thermometers  are  at  212°,  the  index, 
m,  is  again  observed.  The  difference  indicates  the  dilata- 
tion of  the  air  for  180°;  and  in  this  manner  Gay-Lussac 
found  that  100  volumes  of  air  become  1375.  These  re- 
sults have  been  of  late  carefully  examined  by  Rudberg,  who 
fixes  the  amount  of  expansion  of  air  at  of  its  volume, 
at  32°,  for  every  degree  of  Fahrenheit’s  scale. 


LECTURE  XLYI. 

Compounds  of  Nitrogen  and  Oxygen. — Protoxide  of 
Nitrogen. — Prejparation  and Pro'perties  of. — Constitu- 
tion.— Supports  Combustion. — Produces  Intoxication. 
Deutoxide  of  Nitrogen. — Preparation  and  Properties 
of — Constitution. — Relations  to  free  Oxygen. — Hypo- 
nitric  Acid. — Preparation  and  Properties  of. 

PROTOXIDE  OF  NITROGEN.  NO  = 22*203. 

If  the  nitrate  of  ammonia  be  exposed  to  a temperature 
of  about  350  degrees  in  a retort.  Fig.  216,  it  undergoes 
decomposition,  being  resolved  into  water  and  the  protoxide 
of  nitrogen  ; the  former  condensing  in  the  neck  of  the  retort, 
and  the  latter  rising  into  the  pneumatic  jar.  If  whitish 


What  is  the  absolute  dilatation  of  air  as  determined  by  Rudberg  ? How 
may  protoxide  of  nitrogen  be  made  ? 


214 


PROTOXIDE  OF  NITROGEN. 


Fig.  216.  fumes  are  evolved,  they  indicate 

that  the  process  is  going  on  too  fast, 
and  the  heat  must  then  he  moder- 
ated. The  change  taking  place  is 
very  simple.  It  is  a mere  re-ar- 
rangement of  the  constituent  atoms 
of  the  nitrate  of  ammonia. 

NO,  + TO  . 2{NO)  -f  3(iTO). 

One  atom  of  that  salt,  therefore,  yields  two  atoms  of  protox- 
ide of  nitrogen  and  three  of  water. 

The  protoxide  of  nitrogen  is  a colorless  gas,  transparent, 
like  atmospheric  air ; it  has  a sweetish  taste,  and  is  soluble 
in  water,  that  liquid  taking  up  about  three  fourths  of  its 
volume  of  the  gas  when  cold,  hut  the  solvent  power  being 
greatly  diminished  by  warming  the  water.  Its  specific  grav- 
Fig.2V7.  ity  is  1-527.  It  may  be  liquefied  at  45^  by  a press- 
ure of  fifty  atmospheres,  and  has  even  been  solidi- 
fied. In  the  liquid  form  it  is  colorless,  and  boils  at 
— 125^.  A drop  of  it  falling  on  the  skin  produces, 
as  it  were,  a burn.  Water  put  in  contact  with  it 
instantly  freezes.  If  the  liquid  be  permitted  to  es- 
cape into  the  air  from  a jet,  a part  of  it  instantly 
freezes  into  a snowy  solid.  It  is  composed,  by  atom, 
of  one  of  nitrogen  and  one  of  oxygen,  and  by  volume,  of  two 
volumes  of  nitrogen  united  to  one  of  oxygen,  condensed  into 
two  volumes,  a constitution  like  that  of  water.  It  therefore 
contains  half  its  bulk  of  oxygen  gas,  and  supports  combustion 
with  activity.  A lighted  taper  immersed  in  it  burns  brightly, 
and,  as  in  oxygen,  if  there  be  merely  a spark  on  the  wick, 
it  kindles  into  a flame.  Phosphorus  burns  in  it  with  great 
brilliancy. 

Sir  H.  Davy  discovered  that  not  only  does  this  gas  sup- 
port respiration,  but  that  it  exerts  a remarkable  physiolog- 
ical action  when  breathed,  producing  a transient  intoxica- 
tion, which  wears  off  after  two  or  three  minutes.  These 
cflects  are  undoubtedly  due  to  the  oxydizing  action  which 
the  protoxide  establishes  in  the  system.  In  this  respect  it 
is  far  more  active  than  even  pure  oxygen  gas,  and  the  rea- 
son is  obvious  : oxygen  is  but  slightly  absorbable  by  watery 
fluids,  but  this  gas  is  taken  up  by  them  to  a very  great  ex- 

What  are  the  properties  of  protoxide  of  nitrogen  ? What  is  its  constitu- 
tion ? Does  it  support  combustion  ? What  are  its  relations  to  respiration  ? 
How  long  does  this  intoxicating  effect  last  ? V/hat  is  the  cause  of  it  ? . 


DEUTOXIDE  OF  NITROGEN.  ^ 215 

tent.  When  it  is  introduced  into  the  lungs,  it  is  rapidly 
dissolved  in  the  blood,  and  carried  by  the  circulation  to  every 
part  of  the  body,  oxydizing  whatever  is  in  its  path,  and  pro- 
ducing a febrile  warmth  and  an  unusual  mental  disturbance. 

The  protoxide  of  nitrogen  shows  but  little  disposition  to 
unite  with  other  bodies.  It  may  be  regarded  as  an  indif- 
ferent substance. 

DEUTOXIDE  OF  NITROGEN.  = 30-216. 

The  deutoxide  or  binoxide  of  nitrogen  may  be  made  by 
the  action  of  nitric  acid  moderately  diluted  upon  metallic 
copper.  If  these  substances  are  introduced  into 
a flask  together,  and,  when  the  action  mod- 
erates, fresh  portions  of  nitric  acid  be  added 
through  the  funnel  {Fig.  218),  a colorless  gas 
is  evolved,  which  may  be  collected  over  wa- 
ter, in  which  it  is  only  sparingly  soluble,  one 
hundred  volumes  of  that  liquid  dissolving  about 
five  of  the  gas. 

It  is  composed  of  equal  volumes  of  nitrogen 
and  oxygen  united,  without  condensation.  Its  specific  grav- 
ity is,  therefore,  T0416.  It  does  not  support  combustion; 
a lighted  taper  immersed  in  it  is  at  once  extinguished  ; but 
if  phosphorus,  burning  violently,  be  introduced  in  it,  the 
combustion  goes  on  with  increased  activity.  Iron  and  sev- 
eral other  metals  withdraw  from  it  one  half  of  its  oxygen, 
converting  it  into  the  protoxide. 

The  most  remarkable  quality  of  the  deutoxide  of  nitrogen 
is  its  action  on  mixtures  containing  oxygen  gas,  as,  for  ex- 
ample, atmospheric  air  ; with  these  it  at  once  produces  red 
fumes  of  nitrous  acid,  which  are  soon  removed  if  water  be 
present,  the  deutoxide  taking  up  two  atoms  of  oxygen  to 
change  into  nitrous  acid.  On  this  principle  it  has  been  used 
for  the  purpose  of  effecting  the  analysis  of  atmospheric  air, 
but,  unless  several  precautions  are  observed,  the  results  are 
incorrect.  The  deutoxide  should  be  added  in  a small  and 
steady  stream  to  the  air ; red  fumes  are  at  once  produced ; 
these  are  soon  removed  by  the  water,  and  the  residue  is  less 
in  volume  than  the  air  and  deutoxide  taken  together.  One 
fourth  of  the  deficit  is  equal  to  the  volume  of  the  oxygen 

Why  is  the  protoxide  of  tiitrogen  an  indifferent  substance  ? How  is  the 
deutoxide  obtained  ? What  is  its  constitution  ? Does  it  support  combus- 
tion ? What  is  its  action  on  gaseous  mixtures  containing  oxygen  ? Under 
what  circumstances  may  it  be  used  to  determine  the  amo’.int  of  oxygen? 


Fig.  218. 


216 


HYPONITROUS  ACID. 


# 

originally  present.  By  operating  in  this  manner,  as  I have 
had  many  occasions  to  observe,  correct  results  may  he  ob- 
tained. The  general  process  may  he  illustrated  by  taking 
a tall  jar  and  placing  in  it  a certain  volume  of  atmospheric 
air,  to  'which  is  to  he  added  an  equal  volume  of  the  deutox- 
ide.  Though  both  gases  are  colorless  at  first,  a deep  cop- 
per-colored vapor  is  the  result ; this  is  removed  after  a time 
by  the  action  of  the  water,  which,  rising  in  the  jar,  exhib- 
its a deficit  in  the  amount  of  the  gases. 

A solution  of  the  protosulphate  of  iron  dissolves  this  gas 
abundantly  ; and  if  a small  quantity  of  the  sulphuret  of  car- 
bon be  poured  into  it,  and  a light  applied,  the  mixture  burns 
with  a blue  flame. 

HYPONITROUS  ACID.  NO^  = 38-229. 

This  substance  may  be  made  by  mixing  four  volumes  of 
dry  deutoxide  of  nitrogen  with  one  of  dry  oxygen,  and  ex- 
posing the  mixture  to  cold.  The  gases  condense  into  a liq- 
uid of  a greenish  color,  which  gives  forth  an  orange  vapor. 
Hyponitrous  acid  is  decomposed  by  the  contact  of  water, 
deutoxide  of  nitrogen  escaping  with  an  effervescence,  and 
nitric  acid  being  produced,  three  atoms  of  hyponitrous  acid 
yielding  one  of  nitric  acid  and  two  of  the  deutoxide. 
ZNO^.,.=:,..NO,  + 2NO^, 


LECTURE  XLVIL 

Compounds  of  Nitrogen  and  Oxygen. — Nitrous  Add. — 
Preparation  and  Properties  of. — Kemarhahle  Changes 
of  Color. — Nitric  Acid. — Discovery  of. — Cavendish's 
Experiments.  — Sources  from  which  it  is  derived.  — 
Commercial  Preparations. — Its  Properties. — Is  a Hy- 
pothetical Body. — Purification. — Detection . 

NITROUS  ACID.  NO^  = A6-242. 

Nitrous  acid  may  be  made  by  mixing  together  one  vol- 
ume of  dry  oxygen  with  two  of  the  dry  deutoxide  of  nitro- 
gen, and  exposing  the  mixture  to  a very  low  temperature  ; 

How  may  the  action  of  deutoxide  of  nitrogen  on  oxygen  mixtures  be  illus- 
trated ? What  is  its  relation  with  the  protosulphate  of  iron  ? And  what  with 
the  vapor  of  sulphuret  of  carbon  ? How  may  hyponitrous  acid  be  procured  ? 
What  is  the  action  of  water  on  it  ? How  may  nitrous  acid  be  made  ? 


NITROUS  ACID.  217 

but  it  is  much  more  easily  procured  by  distilling,  in  a por- 
celain, or  hard  glass  retort,  Fig. 

219,  dry  nitrate  of  lead,  and  receiv- 
ing the  gases  in  a tube,  b,  artificially 
cooled  by  a freezing  mixture,  c.  The 
nitrous  acid  condenses  as  a colorless 
liquid,  which  becomes  yellow  as  its 
temperature  rises.  Its  specific  grav- 
ity, in  the  liquid  form,  is  1*42.  It  solidifies  at  40°  F.,  and 
boils  at  82°  F.  Its  vapor  possesses  remarkable  optical 
qualities.  "When  its  temperature  is  very  low,  it  is  nearly 
colorless  ; it  takes  on  an  orange  tint  as  the  degree  of  heat 
increases,  and  finally  becomes  almost  black.  The  peculiar- 
ity of  the  phenomenon  is,  that  if  the  gas  be  examined  while 
undergoing  these  changes,  by  passing  a ray  of  light  through 
it  and  analyzing  it  by  means  of  a prism,  as  explained  in 
Lecture  XX.,  a great  number  of  fixed  lines  are  found  in  the 
resulting  spectrum  ; and  as  the  temperature  rises,  these  in- 
crease so  much  in  number  and  in  breadth  that  the  light  be- 
comes finally  obliterated. 

* The  vapor  of  nitrous  acid,  when  once  mixed  with  atmos- 
pheric air,  is  condensed  into  the  liquid  form  with  great  dif- 
ficulty. It  is  wholly  irrespirable,  and,  even  when  diluted, 
of  a very  unpleasant  odor.  Nitrous  acid  is,  for  the  most 
part,  decomposed  by  water, 

3iVO^  ...  = ...  2NO^  + iV02, 
three  atoms  of  it  yielding  to  two  of  nitric  acid  and  one  of 
the  deutoxide  of  nitrogen,  as  seen  in  the  formula ; but  the 
nitric  acid  produced  protects  a portion  of  the  nitrous  acid, 
which  thus  escapes  decomposition.  Its  vapor  is  absorbed  by 
nitric  acid.  The  production  of  this  acid  by  the  process  with 
nitrate  of  lead  is  of  considerable  philosophical  interest ; 

FbO  + NO,  PbO  + NO^  + O,  • 

one  atom  of  the  nitrate  of  lead  yielding  one  atom  of  oxide 
of  lead,  which  remains  in  the  retort,  one  of  nitrous  acid,  and 
one  of  oxygen  gas,  which  escape.  It  might  be  expected  that, 
in  such  a distillation,  we  should  obtain  oxide  of  lead  and 
nitric  acid.  The  cause  of  the  non-appearance  of  the  latter 
body  will,  however,  be  presently  understood. 

I What  are  its  properties  ? How  does  the  color  of  its  vapor  change  by- 
heat  ?•  What  is  the  cause  of  the  final  blackness  ? What  are  the  relations 
of  nitrous  acid  and  water?  What  is  the  decompositionwhich  takes  place, 
when  nitrate  of  lead  is  distilled?  ~ " > 

K 


218 


NITKIC  ACm, 


NITRIC  ACID.  NOs  = 54  255. 

Nitric  acid,  the  most  important  of  the  compounds  xxf  oxy- 
gen and  nitrogen,  and  one  of  the  most  important  of  the  acid 
bodies,  was  first  discovered  during  the  ninth  century.  The 
discovery  of  this  and  some  of  the  other  powerful  acids  form 
one  of  the  epochs  in  chemistry.  The  science  can  scarcely  be 
said  to  have  existed  until  that  time,  the  Egyptians,  Greeks, 
and  Romans  having  no  knowledge  of  these  bodies,  nor,  in- 
deed, of  any  more  powerful  than  vinegar. 

The  constitution  of  nitric  acid  was  determined  by  Mr. 
Cavendish,  who  formed  it  synthetically  by  passing  electric 
sparks  through  atmospheric  air  in  contact  with  a solution 
of  pota:sh.  The  nitrate  of  potash  was  obtained. 

Nitric  acid  also  occurs  to  a small  extent  in  rain  water, 
especially  after  thunder  storms,  and  by  some  supposed  to 
originate  upon  the  same  principles  as  in  Cavendish’s  experi- 
ments ; but  probably  it  is  due  to  the  oxydation  of  ammonia, 
which  always  exists  in  the  air.  The  chief  supply  is  derived 
indirectly  from  the  decay  of  vegetable  or  animal  matter,  in 
the  presence  of  oxygen  gas,  and  in  contact  with  basic  bod- 
ies. Collections  of  such  refuse  pass  under  the  name  of  ni- 
tre beds,  and,  in  France  and  Germany,  furnish  the  saltpetre 
which  is  used  for  the  manufacture  of  gunpowder.  In  the 
East  Indies,  nitrate  of  potash  is  obtained  by  lixiviation 
from  the  soil  in  which  earthy  nitrates  naturally  occur. 
From  South  America  the  nitrate  of  soda  is  exported  ; it  is 
found  as  an  efEorescence  on  soils  in  which  common  salt  prob- 
ably exists. 

In  most  of  these  cases  the  nitric  acid  arises  from  the  oxy- 
dation of  ammonia  produced  during  putrefactive  ferment- 
ation. 

iViTg  + Og  . iVDs  + 3HO. 

The  formula  shows  the  probable  nature  of  the  action  ; one 
atom  of  ammonia,  under  the  influence  of  eight  of  oxygen, 
will  yield  one  of  nitric  acid  and  three  of  water. 

The  nitric  acid  of  commerce  is  made  by  distilling  equal 
weights  of  sulphuric  acid  and  nitrate  of  potash.  The  pro- 
cess may  be  conducted  in  a small  way  in  a glass  retort.  A, 
Fig.  220  ; and  it  is  found  advantageous  to  use  the  quantity 

When  was  nitric  acid  discovered  ? How  was  its  composition  determined 
by  Cavendish?  What  is  the  source  of  the  nitric  acid  in  rain  water?  From 
what  sources  is  nitrate  of  potash  produced  ? How  may  nitric  acid  arise 
from  the  oxydation  of  ammonia  ? How  may  nitric  acid  be  made  ? 


NITRIC  ACID. 


219 


Fig,  220. 


of  sulphuric  acid  here  stated,  because  a soluble  bisulphate 
of  potash  is  formed,  which  may  be  easily  removed  without 
breaking  the  retort.  Half  as  much  sulphuric  acid  would 
effect  the  decomposition,  but  it  would  require  a higher  tem- 
perature, and  the  neutral  sulphate  which  forms  could  with 
difficulty  be  removed.  The  change  Avhich  takes  place  is 
thus  exhibited : 

(/fO,  NO,)  + 2(  JJO,  80^)  (ifO,  HO,  280,) 

+ {HO,NO,^,) 

that  is,  one  atom  of  nitrate  of  potash  and  two  of  sulphuric 
acid  furnish  one  atom  of  bisulphate  of  potash,  and  one  of 
hydrated  nitric  acid  distills  over  into  the  receiver,  B,  which 
is  kept  cool  by  a stream  of  Avater  flowing  from  i into  a A^es- 
sel,  c c,  the  Avaste  water  passing  through  led.  A net  is 
wrapped  over  the  receiver  to  distribute  the  water  evenly. 
In  this  process  nitrate  of  soda  may  be  advantageously  sub- 
stituted for  nitrate  of  potash. 

Hydrated  nitric  acid  thus  produced  is  a colorless  liquid, 
which  boils  at  248°  F.,  though  this  point  changes  with  the 
amount  of  water  in  the  acid.  It  freezes  at  — 40°  ; is  de- 
composed into  oxygen  and  nitrogen  by  being  passed  through 
a red-hot  glass  tube.  It  turns  yellow  in  the  sunshine,  oav- 
ing  to  a portion  being  decomposed  and  nitrous  acid  set  free, 
which  dissolves  in  the  residue,  and  gives  it  an  orange  tint. 
The  nitric  acid  of  the  shops  (aqua  fortis)  commonly  possess- 
es this  color,  from  which  it  may  be  freed  by  boiling  in  a 
glass  vessel.  It  stains  the  skin  and  other  organic  matters 

What  are  its  properties?  When  passed  through  a red-hot  tube,  what 
happens  to  it  ? Why  is  commercial  nitric  acid  often  yellow  ? What  is  the 
action  of  this  acid  on  the  skin  and  on  metallic  bodies  ? 


220 


PROPERTIES  OF  NITRIC  ACID. 


yellow,  and  hence  is  used  in  the  arts  of  dyeing.  Its  action 
on  many  metalline  and  other  combustible  bodies  is  exceed- 

Fi^.  221.  ingly  violent,  owing  to  the  great  amount  of  oxygen 
it  contains.  Poured  upon  some  pieces  of  copper 
in  a wine-glass,  over  which  a bell  jar  may  be 
inverted  {Fig.  221),  an  effervescence  takes  place, 
and  the  red  fumes  of  nitrous  acid  abundantly  form. 
Though  it  is  one  of  the  most  powerful  oxydizing 
agents  we  possess,  it  often  happens  that,  in  a 
state  of  great  concentration,  it  will  scarcely  act  on  a metal, 
but  the  addition  of  a little  water  causes  the  action  to  set  in. 

Nitric  acid  (iV'Og)  was,  until  recently,  regarded  as  a hy- 
pothetical or  imaginary  body,  the  nearest  approach  to  it 
being  the  strongest  aqua  fort  is  ; this  has  a specific  gravity 
of  1*521,  and  consists  of  one  atom  of  hypothetical  nitric  acid 
and  one  of  water.  Its  formula,  therefore,  is 

KO^  + HO. 

Its  molecular  constitution  probably  is 

NO,+H. 

It  is,  as  we  shall  find  hereafter,  a hydrogen  acid.  But 
M.  Deville  has  shown  that  the  anhydrous  acid  may  be  pre- 
pared by  the  action  of  chlorine  or  dry  nitrate  of  silver.  It 
presents  the  form  of  colorless  crystals,  which  melt  at  about 
85®,  the  boiling  point  being  113®,  and  gradually  decomposes 
at  ordinary  temperatures. 

Nitric  acid  of  commerce  can  be  purified  by  distillation, 
rejecting  the  first  portions  which  come  over,  as  they  contain 
chlorine,  and  leaving  a portion  in  the  retort  containing  sul- 
phuric acid  and  fixed  impurities.  If  twelve  parts  are  dis- 
tilled, the  first  three  may  be  cast  aside,  and  one  left  in  the 
retort ; the  intermediate  eight  are  pure. 

"When  it  is  in  a solution,  nitric  acid  may  be  detected  by 
the  addition  of  sulphuric  acid,  and  a drop  or  two  of  proto- 
sulphate of  iron  ; a' brownish  color  is  produced  where  the 
two  liquids  meet.  When  in  a concentrated  state,  the  evo- 
lution of  red  fumes,  by  the  action  of  copper,  detects  it.  It 
also  gives  a blood-red  color  with  morphia.  The  nitrates 
deflagrate  when  ignited  with  combustible  matter;  a result 
which  may  be  well  shown  by  grinding  together  a few 
ounces  of  nitrate  of  potash  and  common  sugar,  and  setting 


What  is  the  nearest  approach  to  hypothetical  nitric  acid  ? Why  can  not 
it  be  isolated  T How  may  it  be  purified  ? How  may  it  be  detected  ? 


SULPHUR.  221 

fire  to  the  mixture.  Owing  to  the  solubility  of  all  its  com- 
pounds, nitric  acid  can  not  he  precipitated. 


LECTURE  XLYIIL 

Sulphur. — Natural  and  Artificial  Forms. — Frcparation 
of  Flowers. — Properties  of  Sulphur. — Its  Vapor. — 
Oxygen  Compounds  of  Sulphur. — Sulphurous  Acid. — 
Preparation. — Properties. — Bleaching  E ffects. — Con- 
densation  to  the  Liquid  State. — Its  Compounds. 

SULPHUR.  fclG-12. 

Much  of  the  sulphur  in  commerce  is  derived  from  vol- 
canic countries,  in  which  it  occurs  often  in  a pure  and  crys- 
tallized state.  It  is  one  of  the  most  common  elementary 
substances,  being  found  abundantly  united  with  various 
metals,  such  as  iron,  copper,  lead.  In  combination  with 
lime,  baryta,  &c.,  it  occurs  as  sulphuric  acid,  and  is  also 
an  ingredient  of  many  animal  and  vegetable  products. 

Sulphur  is  met  with  under  three  different  forms  : roll 
sulphur,  flowers  of  sulphur,  and  lac  sulphuris.  Roll  sulphur 
is  an  impure  variety,  which  receives  its  form  from  being 
cast  into  ’cylindrical  moulds  ; the  flowers  of  sulphur  are 
formed  from  the  impure  brimstone  by  sublimation  ; lac  sul- 
phuris differs  from  the  foregoing  in  being  of  a white  color. 
It  is  prepared  by  precipitation  from  the  persulphuret  of  po- 
tassium by  hydrochloric  acid. 

The  preparation  of  flowers  of  sulphur  is  conducted  in  an 
apparatus,  such  as  Fig.  222.  A is  a room,  or  chamber,  of 


Why  can  not  nitric  acid  be  detected  by  precipitation  ? Under  what  forms 
does  sulphur  naturally  occur  ? What  are  its  artificial  forms  ? How  are 
the  flowers  of  sulphur  made  ? 


222 


PROPERTIES  0P  SULPHUR. 


2000  feet  capacity ; c is  a pan  containing  sulphur,  which 
is  melted  by  the  furnace,  os;  the  vapor  passes  along  i cl  5, 
and,  entering  the  chamber,  is  there  condensed.  The  re- 
sulting flowers  are  removed  through  the  door  p.  If  an  ex- 
plosion occurs,  when  the  process  commences,  it  lifts  the 
valve  e,  and  the  gases  escape  through  the  chimney,  t.  M 
ikZ"  is  a shed  under  which  the  apparatus  is  constructed.  As 
the  iron  pan  becomes  exhausted,  new  quantities  of  brim- 
stone can  be  introduced  through  the  door  n. 

Sulphur  commonly  exists  as  a solid  of  a yellow  color, 
and  of  a specific  gravity  of  1*99,  having  neither  taste  nor 
smell.  It  melts  at  226°  F.  into  a pale  yellow-colored 
liquid  ; but,  what  is  very  curious,  if  the  heat  be  raised  to 
about  450°  F.,  it  changes  to  the  color  of  molasses,  and  be- 
comes so  thick  and  tenacious  that  the  capsule  in  which  the 
fusion  is  carried  on  may  be  turned  upside  down  without  the 
sulphur  flowing  out.  At  600°  F.  it  boils,  and,  as  the  heat 
approaches  that  point,  it  again  becomes  fluid ; and,  as  it 
cools,  runs  through  the  same  changes  again  in  a reverse  or- 
der. If  suddenly  quenched  in  cold  water  at  the  low  tem- 
perature, before  it  thickens,  it  solidifies  into  ordinary  sul- 
phur ; but  if  heated  for  a time  to  near  600°,  and  then 
quenched,  it  becomes,  on  cooling,  elastic,  like  India-rubber, 
and  may  be  drawn  into  long  threads ; and  in  this  state  is 
sometimes  used  for  taking  casts  of  coins,  for  by  keeping  a 
few  days  it  slowly  returns  to  the  condition  of  ordinary  sul- 
phur. 

When  rubbed  on  a piece  of  flannel  it  becomes  highly  elec- 
tric, assuming  the  negative  state,  and  at  one  time  was  used 
in  the  making  of  electrical  machines,  before  the  powers  of 
glass  were  discovered.  A roll  of  it  held  in  the  warm  hand 
emits  a crackling  sound,  the  crystals  of  which  it  is  com- 
posed separating  from  one  another.  It  is  a bad  conductor 
of  heat  and  electricity,  crystallizes  under  two  different  sys- 
tems, and  is,  therefore,  a dimorphous  body,  one  of  its  forms 
being  an  acute  rhombic  octahedron,  and  the  other  an  oblique 
rhombic  prism.  When  heated  to  about  300°  F.  in  the  open 
air,  it  takes  fire,  and  burns  with  a blue  flame,  emitting  a 
suffocating  odor,  fumes  of  sulphurous  acid  gas.  It  is  wholly 

What  are  the  properties  of  sulphur?  What  changes  may  be  observed  in 
it  when  melting  ? What  electrical  condition  does  it  assume  by  friction  ? 
What  are  its  conducting  powers  ? Why  is  it  called  a dimorphous  body? 
At  what  temperature  does  it  take  fire,  and  what  is  the  product  of  its  com^ 
bustion? 


SULPHUROUS  ACID.  223 

insoluble  in  water  ; its  proper  solvent  is  the  bisulphuret  of 
carbon. 

The  vapor  of  sulphur  is  of  a deep  yellow  color,  and  has 
the  high  specifie  gravity  of  6 '648.  In  it  metallic  bodies 
will  burn  precisely  as  they  do  Fig.  m 

in  oxygen  gas.  Dr.  Hare  has 
shown  that  if  a gun  barrel  be 
heated  red  hot  at  the  breech, 
and  a piece  of  sulphur  dropped 
into  it,  the  muzzle  being  closed 
with  a cork,  an  ignited  jet  of 
sulphur  vapor  issues  from  the  touch-hole,  in  which,  if  a 
bunch  of  iron  wire  be  held,  it  takes  fire  and  burns  brilliantly. 

Sulphur  has  a very  extensive  range  of  affinities,  uniting 
with  most  metallic  substances  in  several  different  propor- 
tions, with  hydrogen  and  also  with  oxygen.  With  the  lat- 
ter substance  it  furnishes  the  following  compounds : 

SO^ . . SO3 . . 

their  designations  are,  respectively, 

Sulphurous  acid. 

Sulphuric  acid. 

Hyposulphurous  acid. 

Hyposulphuric  acid. 

Sulphureted  hyposulphuric  acid  (acid  ofXianglois). 

Bisulphureted  hyposulphuric  acid  (acid  of  Fordos  and  Gelis). 

SULPHUROUS  ACID.  = 32  146. 

This  acid  may  be  formed  by  burning  sulphur  Fig.  224. 
in  oxygen  gas  or  in  atmospheric  air ; in  the  lat- 
ter instance  the  resulting  gas  is,  of  course,  con- 
taminated with  nitrogen.  The  process  may  be 
conducted  under  a bell  jar,  the  burning  sulphur 
being  placed  on  a capsule  or  stand. 

But  a much  better  process  is  to  effect  the  par- 
tial deoxydation  of  sulphuric  acid  by  heating 
oil  of  vitriol  with  mercury,  which  deprives  it  of 
one  atom  of  oxygen,  forming  an  oxide  of  mercury,  which 
unites  with  one  atom  of  the  excess  of  sulphuric  acid  pres- 
ent to  form  a sulphate.  For  many  of  the  ordinary  purposes 
to  which  sulphurous  acid  is  applied,  it  may  be  procured  by 
the  action  of  fragments  of  charcoal  heated  with  sulphuric 

What  is  the  specific  gravity  of  its  vapor?  Does  it  support  combustion? 
What  are  the  oxygen  compounds  of  sulphur  ? How  may  sulphurous  acid 
be  made  ? What  is  the  principle  of  the  process  when  sulphuric  acid  acts 
on  mercury  or  charcoal  ? 


224 


SULPHUROUS  ACID. 


acid.  In  this  case,  however,  carbonic  acid  is  also  evolved. 
When  a solution  in  water  is  required,  the  gas  may  be  pass- 
ed directly  into  that  liquid,  but  if  it  be  necessary  to  retain 
it  in  a gaseous  state,  it  must  be  received  in  jars  at  the  mer- 
curial trough,  or  collected  by  the  method  of  displacement. 

It  is,  under  the  ordinary  circumstances,  a transparent  and 
Fig.  225.  colorless  gas,  having  an  unpleas- 

ant taste,  and  the  smell  charac- 
teristic of  burning  sulphur.  It  is 
wholly  irrespirable,  and  prompt- 
ly extinguishes  a lighted  taper. 
Its  specific  gi'avity  is  2*222,  and, 
therefore,  if  a stream  of  it  which 
has  been  cooled  by  flowing  from 
the  generating  flask  a.  Fig.  225, 
through  a bent  tube,  h,  immersed  in  a jar  of  cold  water,  be 
conducted  to  the  bottom  of  another  jar,  c,  the  gas,  as  it  col- 
lects, displaces  the  atmospheric  air,  floating  it  out  of  the  ves- 
sel. This  process  is  of  very  general  application  in  the  col- 
lection of  gases  which  are  absorbable  by  water,  and  is  known 
under  the  name  of  the  method  by  displacement. 

In  a jar  of  sulphurous  acid  thus  collected,  if 
a lighted  taper  be  immersed,  it  is  at  once  extin- 
guished. If  the  jar  be  inverted  over  water,  the 
gas  is  speedily  dissolved,  that  liquid  taking  up 
about  thirty-seven  times  its  volume  of  the  gas. 
If  vegetable  colors  are  submitted  to  its  influence, 

1 they  are  bleached,  but  the  color  is  not  destroyed 
as  in  bleaching  by  chlorine,  since  it  can  be  re- 
stored by  the  action  of  a stronger  acid. 

Sulphurous  acid  is  among  the  gases  one  that  most  readily 
takes  the  liquid  form.  If  there  be  connected  with  the  flask 
from  which  this  gas  is  being  evolved  a bent  tube  passing 
through  iced  water  in  a jar,  and  the  gas,  after  traversing* 
this  tube,  be  conducted  into  a bottle  placed  in  a freezing 
mixture  of  snow  and  dilute  nitric  acid,  it  condenses  into  a 
colorless  fluid  of  the  specific  gravity  1*45,  which  boils  at 
14^  F.  This  fluid  is  sometimes  used  to  produce  intense 
cold  by  its  evaporation. 

What  are  the  products  in  each  case  ? Vv^hy  must  the  gas  be  collected 
over  mercury  ? What  are  it?  properties  ? What  is  the  method  by  displace- 
ment? To  what  extent  is  this  acid  soluble  in  water?  Are  its  bleaching 
effects  permanent  ? How  may  it  be  condensed  ? 


Fig.  226. 


SULPHURIC  ACID. 


225 


With  bases,  this  acid  forms  a complete  series  of  salts, 
the  sulphites,  which  are  readily  decomposed  by  the  stronger 
acids,  and  are  occasionally  employed  as  deoxydizing  agents, 
from  the  circumstance  that  metallic  oxides  may  be  reduced 
by  them,  their  sulphurous  passing  into  the  condition  of  sul- 
phuric acid. 


LECTURE  XLIX. 

Compounds  of  Sulphur  and  Oxygen. — Sulphuric  Add, 
— The  Anhydrous  Acid.  — Its  Affinity  for  Water. — 
German  Oil  of  Vitriol. — Its  Constitution  and  Uses. — 
Common  Sulphuric  Acid. — Preparation  on  the  large 
Scale. — Its  Chemical  Relations. — Purification. — De- 
tection.— Other  Sulphuric  Acids. 

SULPHURIC  ACID.  ^03  = 40159. 

This  compound  is  not  alone  the  most  important  of  the 
acids  of  sulphur,  but  also  the  most  important  of  all  acids. 
By  the  aid  of  it,  nitric,  hydrochloric,  and  many  other  strong 
acids  are  made  for  commercial  purposes.  In  the  production 
of  carbonate  of  soda  and  chloride  of  lime,  immense  quanti- 
ties of  it  are  consumed. 

Of  sulphuric  acid  we  have  several  varieties,  differing  from 
each  other  in  the  amount  of  water  they  contain.  1st.  There 
is  anhydrous  sulphuric  acid,  the  formula  for  which  has  al- 
ready been  given  as  containing  one  atom  of  sulphur  and 
three  of  oxygen.  This  substance  may  be  prepared  by  sub- 
mitting the  fuming  oil  of  vitriol  of  Xordhausen  to  a tem- 
perature of  about  290°  Fahr.,  when  there  distills  over  a 
white  substance  of  a crystalline  aspect.  It  fumes  in  the  air, 
melts  at  77°  Fahr.,  is  converted  into  vapor  at  160°,  has  an 
intense  affinity  for  water,  in  which,  if  it  be  placed,  it  hisses 
like  a red-hot  iron.  It  is  to  be  particularly  remarked,  how- 
ever, that  the  acid  powers  of  this  substance  are  very  feebly 
marked  ; it  shows  little  tendency  to  unite  with  other  bodies, 
and  when  such  combinations  are  effected,  the  resulting  sub- 
stances are  different  from  the  true  sulphates. 

What  are  the  properties  of  this  liquid  ? For  what  purposes  are  the  sul- 
phites employed?  What  are  the  properties  of  anhydrous  sulphuric  acid,  and 
now  is  it  prepared  ? 

K 2 


OIL  OF  VITRIOL. 


2(1.  German,  or  Nordhausen  oil  of  vitriol,  HO,  80^  + 
SO3. 

This  substance  is  prepared  by  taking  green  vitriol,  and, 
by  exposure  to  heat,  driving  off  its  water  of  crystallization 
(six  atoms),  and  also  a portion  of  its  saline  water.  If  the 
dried,  powder  be  placed  in  a stone- ware  retort  and  exposed 
to  a high  temperature,  there  distills  over  a dark  oily  liquid ; 
hence  the  term  oil  of  vitriol : this  is  the  substance  in  ques- 
tion. Its  formula  shows  that  it  is  composed  of  two  atoms 
of  anhydrous  acid  united  to  one  of  water.  A considerable 
quantity  of  it  is  used  in  the  arts  for  dissolving  indigo. 

3d.  Common  sulphuric  acid,  HO,  80^. 

This  is  the  substance  which  passes  in  commerce  as  com- 
mon oil  of  vitriol.  It  is  made  on  the  large  scale  by  burning 
sulphur  with  nitrate  of  potash  or  soda,  and  conducting  the 
sulphurous  and  nitrous  acids  which  result  into  large  cham- 
bers lined  with  lead,  in  which  steam  is  thrown,  the  bottom 
of  the  chamber  being  covered  with  water.  The  sulphurous 
acid  takes  oxygen  from  the  nitrous  acid,  reducing  it  to  the 
condition  of  deutoxide  ; but  this  being  done  in  the  presence 
of  atmospheric  air,  which  fills  the  chamber,  the  deutoxide 
instantly  reassumes  the  condition  of  nitrous  acid.  The 
deutoxide,  therefore,  continually  transfers  oxygen  from  the 
atmospheric  air  to  the  sulphurous  acid,  and  brings  it  to  the 
condition  of  sulphuric  acid. 

After  a time,  the  water  at  the  bottom  of  the  chamber  be- 
comes charged  with  sulphuric  acid  ; it  is  then  concentrated 
by  drawing  off  the  excess  of  water  in  platina  or  glass  boilers, 
and  finally  assumes  the  specific  gravity  1*845.  It  is  a 
dense  oily  liquid,  freezes  at  — 15°,  and  boils  at  620°. 

The  attraction  of  common  sulphuric  acid  for  water  is  very 
Fig.  227.  ii^tense.  If  a tube,  containing  some  ether,  be  stirred 
in  a glass  {Fig.  227)  in  which  sulphuric  acid  and 
water  are  being  mixed,  the  temperature  rises  so 
high  that  in  a few  moments  the  ether  boils.  On 
the  same  principle,  it  will  remove  from  most  gases 
which  are  passed  over  it  any  water  they  may  con- 
tain ; and,  as  we  have  seen  in  Lecture  XII.,  water 
may  be  frozen  by  taking  advantage  of  the  rapidity  with 


"What  is  the  process  for  preparing  the  German  oil  of  vitriol  ? What  is  its 
appearance?  For  what  purpose  is  it  used?  What  is  the  process  for  pre- 
paring commercial  sulphuric  acid?  What  are  its  properties  ? What  illus- 
trations may  be  given  of  its  intense  affinity  for  water  ? 


ACIDS  OP  SULPHUR. 


227 


which  sulphuric  acid  will  absorb  its  vapor.  Organic  sub- 
stances may  also  be  charred  by  the  action  of  this  acid  ; for 
example,  woody  fibre  is  a compound  of  carbon  with  the  ele- 
ments of  water,  and  when  acted  upon  by  sulphuric  acid, 
the  carbon  is  set  free,  the  acid  taking  from  it  a portion  of 
its  water. 

Sulphuric  acid  of  commerce  is  never  pure  ; it  contains 
sulphate  of  lead,  derived  in  the  process  of  its  manufacture, 
and  also,  sometimes,  arsenic,  selenium,  and  nitrous  acid. 
From  the  first  it  may  be  purified  by  dilution  with  water,  in 
which  sulphate  of  lead  is  insoluble  ; but  when  required  en- 
tirely pure,  it  must  be  distilled,  the  first  portions  being  re- 
jected. 

The  presence  of  sulphuric  acid  may  be  detected  by  any 
of  the  soluble  salts  of  barium,  such  as  the  chloride  of  barium, 
or  the  nitrate  of  baryta,  the  white  sulphate  of  baryta  pre- 
cipitating insoluble  in  water  and  acids. 

To  black  woolen  clothing  this  acid  communicates  a red- 
dish stain,  removable  by  being  touched  with  ammonia. 

Besides  the  compounds  just  described,  we  have  other  def- 
inite hydrates  of  sulphuric  acid,  thus  : 

(4)  SO^  + 2HO. 

(6)  SO^  + 3HO, 

The  fourth  of  these  has  a specific  gravity  of  T78,  and 
crystallizes  at  39°  Fahrenheit  in  large  and  beautiful  crys- 
tals. The  fifth  has  a specific  gravity  of  1632. 

HYPOSULPHUROUS  ACID,  S^O^  = 4S'266, 
has  not  yet  been  isolated  ; one  of  its  salts,  the  hyposulphite 
of  soda,  is  extensively  used  in  the  Daguerreotype  process  for 
removing  the  sensitive  coating  on  the  plates. 

HYPOSULPHURIC  ACID, 

is  a sirupy  liquid  of  a very  acid  taste,  and  is  not  applied  to 
any  use. 

Besides  these,  we  have  two  other  acids  of  sulphur  : 

Sulphureted  hyposulphuric  acid,  = 88* *475,  discovered  by  Langlois. 
Bisulphureted  hyposulphuric  acid,  = 104*595,  discovered  by  Fordos 
and  Gelis. 

Chemists  are  now  very  generally  agreed  that  all  these 

By  what  substances  is  it  usually  rendered  impure  ? How  may  it  be  pu- 
rified? How  may  it  be  detected?  How  may  sulphuric  acid  stains  on 

*jlothing  be  removed  ? What  other  hydrates  of  this  body  are  there  ? What 
are  the  uses  of  hyposulphurous  acid  ? What  other  sulphur  acids  are  there  I 


228 


SULPHURETED  HYDROGEN. 


compounds  are  to  be  regarded  as  hydrogen  acids — a strik- 
ing departure  from  the  Lavoisierian  doctrines.  They  have 
been  led  to  this  view  by  the  consideration  that  no  well- 
marked  acid  exists  in  which  hydrogen  is  not  found ; that 
all  these  sulphur  acids  possess  the  same  neutralizing  power, 
though  the  quantity  of  oxygen  they  contain  is  so  different. 
They  regard  them  all  as  being  formed  by  the  union  of  one 
:;tom  of  hydrogen  with  a series  of  different  compound  radi- 
cals, as  the  following  table  shows  : 

Sulphurous  acid H-\-  SO3 

Sulphuric  acid iT-f-  O. 

Hyposulphurous  acid S03-\-  S. 

Hyposulphuric  acid O3. 

Acid  of  Langlois iZ-j-  iSOa  >S03  -f- 

Acid  of  Fordos  and  Gelis  . . . Af-{-  “f"  ^2- 

Chlorosulphuric  acid JZ’-j-  ^S'03 -j-  C/. 

Nitrosulphuric  acid jfZ" iS  O3  -f-  NO^. 

lodosulphuric  acid /f-f- /; 

and,  extending  these  views  to  the  constitution  of  other  acids 
generally,  an  acid  is  defined  to  be  “a  compound  of  hydro- 
gen with  a simple  or  compound  radical,  in  which  the  hy- 
drogen may  be  replaced  by  any  other  metal.’* 


LECTUEE  L. 

Sulphur  and  Phosphorus. — Sulphureted  Hydrogen. — 
Mode  of  Preparing  it. — Its  Odor,  Acid  Relations,  and 
other  Properties. — Extensively  used  as  a Test. — Occurs 
in  Nature. — Relations  to  the  Animal  System. — Bisul 
phureted  Hydrogen. — Selenium. — Phosphorus. — Pre- 
pared from  Bones. — Shines  in  the  Dark. — Action  of 
Light. — Comhustihility. — Compounds  with  Oxygeyi. 

SULPHURETED  HYDROGEN.  HS  = 17T2. 
mg.  228.  This  gas  may  be  eagily  prepared  by  the  ac- 
tion of  hot  hydrochloric  acid  on  the  native  sul-' 
phuret  of  antimony  pulverized,  and  may  be 
collected  over  a saturated  solution  of  salt  or 
warm  water.  The  action  of  the  materials' 
being 

S\S^  -f  ^[HCl)  Sb^Cl^  + S{HS) ; 

that  is,  one  atom  of  the  sesquisulphuret  of  an- 

What  is  the  nature  of  the  views  now  held  in  relation  to  the  acids  of  sul- 
)hur,  and  acids  generally  ? Describe  the  process  for  preparing  sulphureted 
lydrogen? 


SULPHURETED  HYDROGEN. 


229 


tlmony  and  three  of  hydrochloric  acid  yield  one  of  the  ses- 
quichloride  of  antimony  and  three  of  sulphureted  hydrogen. 

Sulphureted  hydrogen  is  a colorless  and  transparent  gas, 
having  the  odor  of  rotten  eggs.  It  is  absorbed  by  water 
readily,  that  liquid  taking  up  two  or  three  times  its  volume. 
Its  specific  gravity  is  1*177.  It  is  combustible,  and  229. 
may  readily  be  burned  from  a jet  placed  in  the  flask  in  A 
which  it  is  being  evolved,  the  products  of  its  combus-  y 
tion  being  sulphurous  acid  and  water  ; but  if  the  air  1 
in  which  it  is  burned  be  limited  in  quantity,  water 

alone  is  produced  and  sulphur  deposited.  Its  solu-  ! 

tion  in  water  decomposes  gradually  by  contact  with 
the  air,  the  hydrogen  undergoing  oxydation,  and  the  K 
sulphur  being  set  free.  It  has  the  properties  of  a weak  acid, 
reddening  litmus  feebly,  and  yields  with  metallic  bases  wa- 
ter and  sulphurets  : 

MO  + HS,..  HO  + MS. 
many  of  these  sulphurets  being  insoluble  and  highly  col- 
ored : antimony  gives  an  orange  precipitate ; arsenic  and 
cadmium,  yellow;  lead,  brown;  and  manganese,  flesh-col- 
ored. On  this  principle,  the  presence  of  sulphureted  hydro- 
gen may  be  always  detected  : the  carbonate  of  lead,  for  ex- 
ample, is  blackened;  and  hence,  white  paint  exposed  in 
places  in  which  sulphureted  hydrogen  is  being  evolved  turns 
dark,  and  metallic  silver  tarnishes,  and  finally  becomes 
black.  By  a pressure  of  about  seventeen  atmospheres  the 
gas  may  be  liquefied. 

The  action  of  sulphureted  hydrogen  on  metallic  bodies 
may  be  illustrated  in  a very  interesting  manner  by  writing 
on  a sheet  of  paper  with  a solution  of  acetate  of  lead,  the 
letters  being  invisible  until  exposed  to  a stream  of  this  gas, 
when  they  turn  black.  Its  action  in  producing  precipitates 
may  be  shown  by  conducting  a stream  of  it  through  a solu- 
tion of  tartar  emetic,  arsenious  acid,  or  acetate  of  lead. 

Sulphureted  hydrogen  is  sometimes  naturally  dissolved 
in  spring  water,  constituting  the  mineral  waters  of  various 
places,  as  the  Virginia  Springs.  It  is  also  said  to  be  con- 
tained in  the  brackish  water  of  the  mouths  of  large  rivers, 
due,  perhaps,  to  the  action  of  the  organic  matter  they  con- 

What  are  its  distinctive  properties  ? What  are  the  results  of  its  com- 
bustion ? What  is  the  nature  of  the  precipitates  it  gives  with  metallic  ox- 
ides ? How  may  this  action  be  illustrated  ? Is  this  gas  soluble  in  water  ? 
What  is  the  probable  cause  of  its  occurrence  at  the  mouths  of  large  rivers  ? 


230 


SELENIUM. — PHOSPHORtrS. 


tain  upon  the  sulphates  existing  in  the  sea.  It  has  been 
thought  by  some  authors  that  the  existence  of  this  gas  in 
the  air  of  those  places  is  connected  with  the  fevers  which 
there  prevaiL  Sulphureted  hydrogen  is  exceedingly  pois- 
onous when  respired. 

There  is  another  compound  of  sulphur  and  hydrogen,  the 
constitution  of  which  is  not  precisely  known,  though  it  is 
usually  described  as  bisulphureted  hydrogen,  and  its  formula 
is  therefore  HS2.  In  its  properties  it  is  said  to  have  sev- 
eral analogies  with  the  deutoxide  of  hydrogen. 

SELENIUM.  ^e  = 39-6. 

This  element  was  discovered  by  Berzelius  in  certain  vari- 
eties of  pyrites.  It  is  a rare  substance,  analogous,  in  many 
respects,  to  sulphur.  It  burns  in  the  air,  forming  an  oxide 
which  exhales  the  odor  of  decaying  horseradish. 

PHOSPHORUS.  P = 32. 

A remarkable  substance,  first  discovered  by  Brandt,  and 
how  extensively  procured  from  burned  bones,  in  which  it  oc- 
curs as  a phosphate  of  lime.  It  is  found,  also,  in  other  ani- 
mal products,  being  an  essential  ingredient  in  fibrin  and  al- 
bumen, and  also  in  the  brain  and  nervous  matter. 

To  procure  it,  burned  bones 
are  reduced  to  powder,  and 
digested  with  dilute  sulphuric 
acid  ; the  liquid  is  strained, 
mixed  with  powdered  char- 
coal, and,  when  dry,  introduced 
into  a stone-ware  retort,  a, 
Fig.  230,  to  the  neck  of  which 
a bent  copper  tube,  b,  is  at- 
tached, the  mouth  of  which 
dips  beneath  water.  The  re- 
tort being  now  exposed  in  a 
furnace  to  a white  heat,  half 
the  phosphoric  acid  in  the  mix- 
ture is  deoxydized  by  the  char- 
coal, carbonic  oxide  gas  escap- 
ing, and  phosphorus  distilling  over. 

Phosphorus  is  commonly  transparent  and  colorless.  When 

What  other  compound  of  sulphur  and  hydrogen  is  there  ? What  is  sele- 
nium? From  what  source  is  phosphorus  derived  ? 


PROPERtIfiS  OB'  PHOSPHORUS. 


231 


exposed  to  the  light  it  turns  of  a deep  red,  and  this  takes 
place  in  a vacuum,  or  in  gases  which  have  no  action  on 
the  phosphorus.  In  lustre  and  general  appearance  it  has  a 
waxy  aspect.  Exposed  to  the  air  it  smokes,  and  in  a dark 
place  shines — a property  from  which  its  name  is  derived. 
During  this  slow  oxydation  it  exhales  an  odor  much  resem- 
bling that  experienced  when  an  electrical  machine  is  in 
high  activity.  At  32°  it  is  brittle,  at  1 13°  it  melts,  at  572° 
it  boils,  distilling  over  unchanged,  if  oxygen  be  absent.  But 
in  the  air  it  takes  fire  and  burns  at  about  120°,  with  evo- 
lution of  fiakes  of  anhydrous  phosphoric  acid.  Its  specific 
gravity  is  1 11 . 

From  the  intense  affinity  which  phosphorus  has  for  oxy- 
gen, it  requires  to  be  kept  under  the  surface  of  water.  It 
is  met  with  in  commerce  in  the  form  of  small  sticks,  a 
form  given  to  it  by  melting  it  in  glass  tubes  under  warm 
water,  and  pushing  the  resulting  cylinders  out  as  soon  as 
they  have  set.  If  kept  in  an  opaque  bottle  it  is  white, 
but  it  slowly  turns  more  or  less  red  on  exposure  to  the 
daylight. 

From  the  facility  with  which  it  takes  fire,  it  is  necessary 
to  handle  it  very  carefully,  and  to  avoid  keeping  it  in  con- 
tact with  the  warm  hand  too  long.  A few  particles  of  dry 
phosphorus  placed  between  two  pieces  of  brown  paper  and 
rubbed  with  a hard  body,  take  fire  and  burn  furiously  as 
soon  as  the  papers  are  separated.  It  is  upon  this  principle 
that  it  will  readily  inflame  by  the  heat  of  friction,  that  its 
useful  application  in  the  manufacture  of  friction  matches 
depends.  In  chlorine,  or  the  vapor  of  bromine  and  iodine, 
it  takes  fire  spontaneously. 

The  red  variety  of  phosphorus  is  commonly  regarded  as 
an  allotropic  modification,  or  phosphorus  in  the  passive 
state.  Its  melting  point  is  much  higher  than  that  of  the 
ordinary  phosphorus,  being  higher  than  480°.  It  does  not 
shine  in  the  dark.  Its  specific  gravity  is  1'964.  It  shows 
no  disposition  to  unite  with  sulphur,  and  does  not  oxydize  in 
the  air. 

There  are  several  compounds  of  phosphorus  and  oxygen, 
as  follows : 

What  remarkable  property  does  this  body  possess  ? Why  is  phosphorus 
to  be  kept  under  the  surface  of  water  ? What  is  the  action  of  light  upon 
it  ? What  useful  application  is  made  of  its  ready  combustibility  ? What 
are  the  properties  of  the  red  variety  of  phosphorus  ? How  many  compounds 
of  phosphorus  and  oxygen  are  there  ? 


239 


PHOSPHORUS  AND  OXYGEN. 


F^O  ..FO..  FO^ . . FO,. 

These  are  respectively 

Oxide  of  phosphorus.  I Phosphorous  acid. 

Hypophosphorous  acid.  | Phosphoric  acid. 


LECTURE  LI. 

Compounds  op  Phosphorus  and  Oxygen.  — Oxide  of 
Fhosphorus. — Freparation  of. — Hypophosphorous  and 
Fhosphorous  Acids. — Fhosphoric  Acid. — Three  States 
of  Hydration. — Froperties  of  these  three  Acids. — Their 
Salts. — Fhosphureted  Hydrogen. — Spontaneously  In- 
flammable  and No7i-inflammable  Varieties. — Chlorine. 
— Freparation  of — Its  Relation  to  Combustion  and 
Respiration. 

OXIDE  OF  PHOSPHORUS.  P^O. 

This  oxide  may  he  formed  by  causing 
a stream  of  oxygen  gas,  from  the  tube,  a. 
Fig.  231,  to  be  directed  upon  phosphorus 
under  hot  water  in  a glass,  b.  A brilliant 
combustion  under  the  water  is  the  result, 
with  the  production  of  phosphoric  acid  and 
of  a red  powder,  which  is  the  substance  in 
question. 

HYPOPHOSPHOROUS  ACID,  PO, 
is  very  little  known  ; it  is  formed  when  phosphorus  is  boiled 
in  alkaline  solutions. 

PHOSPHOROUS  ACID,  P03, 

is  formed  during  the  slow  combustion  of  phosphorus  in  the 
air  ; it  may  also  be  produced  by  acting  on  the  sesquichlo- 
ride  of  phosphorus  with  water.  The  solution  of  this  acid 
is  sometimes  used  as  a deoxydizing  agent. 

PHOSPHORIC  ACID,  PO5. 

Anhydrous  phosphoric  acid  is  formed  when  phosphorus 
burns  in  dry  air  or  oxygen  gas  {Fig.  232).  It  condenses  in 

How  is  oxide  of  phosphorus  made  ? What  is  its  appearance  ? How  are 
hypophosphorous  and  phosphorous  acids  produced  ? Under  what  circum- 
stances is  anhydrous  phosphoric  acid  produced  ? 


Fig.  231. 


ACIDS  OF  PHOSPHORUS. 


233 


•white  flakes  of  a snowy  appearance,  and  pos- 
sesses an  intense  affinity  for  water,  in  which, 
if  placed,  it  hisses  like  a red-hot  iron.  It 
can  scarcely  be  said  to  possess  acid  proper- 
ties. Until  it  has  united  with  water,  those 
properties  are  very  feebly  developed. 

With  water,  phosphoric  acid  unites  in 
three  proportions,  producing 


Fig.  232. 


Monobasic  phosphoric  acid  . . PO^-\~  ifO,  or  if-j-POg. 

Bibasic  “ “ . . PO5-I-2PO,  or  2P-|- PO7. 

Tribasic  “ “ . . PO5 3if0,  or  POg. 


These  acids  also  have  the  names  of  metaphosphoric,  pyro- 
phosphoric,  and  common  phosphoric  acids  respectively. 
Either  of  them  may  exist  in  solution  with  water. 

Metaphosphoric,  or  the  monobasic  phosphoric  acid,  may 
be  obtained  by  dissolving  phosphorus  in  dilute  nitric  acid, 
evaporating,  and  exposing  the  residue  to  a red  heat.  It 
may  also  be  obtained  by  dissolving  the  anhydrous  acid  in 
water,  evaporating  and  igniting  it.  In  both  these  cases  a 
transparent  body,  like  ice  or  glass,  is  produced  ; hence  called 
glacial  phosphoric  acid.  It  contains  one  atom  of  water, 
which  can  not  be  removed  from  it  by  heat. 

Monobasic  phosphoric  acid  is  characterized  by  giving  a 
white  granular  precipitate  with  nitrate  of  silver ; it  also 
coagulates  albumen,  producing  white  curds.  If  kept  in  a 
solution  of  water,  or  boiled  with  it,  it  passes  into  the  tribasic 
state. 

Pyrophosphoric,  or  bibasic  phosphoric  acid,  may  be  ob- 
tained by  heating  the  common  phosphoric  acid  to  417°  F. 
for  some  time.  In  solution  it  neither  precipitates  silver  nor 
coagulates  albumen,  but  its  salts  yield,  with  silver,  a ffaky 
white  precipitate.  Like  the  former,  this  turns  into  the  tri- 
basic acid  by  boiling  with  water. 

Common,  or  the  tribasic  phosphoric  acid,  may  be  obtained 
from  bone  earth  by  the  action  of  the  oil  of  vitriol,  which 
yields  a precipitate  of  sulphate  of  lime  ; or,  more  easily,  by 
boiling  a solution  of  the  anhydrous  phosphoric  acid.  In  so- 
lution it  neither  precipitates  silver  nor  coagulates  albumen, 
but  its  salts  yield  a Canary-yellow  precipitate  with  the  ni- 


How  many  compounds  does  it  yield  with  water  ? How  is  metaphosphor- 
ic acid  made  ? What  is  g^lacial  phosphoric  acid?  What  are  the  properties 
, characteristic  of  monobasic,  bibasic,  and  tribasic  phosphoric  acids  respect- 
ively ? 


234 


PHOSPHURETED  HYDROGEN. 


Irate  of  silver.  By  exposure  to  a low  heat  it  becomes  bi- 
basic,  and  to  a red  heat,  monobasic. 

These  hydrogen  acids  of  phosphorus  give  rise  to  a very 
extensive  and  complex  class  of  salts,  according  to  the  ex- 
tent to  which  their  hydrogen  is  replaced  by  metallic  bodies. 
Thus  the  monobasic  phosphoric  acid  can  yield  only  one 
series  of  salts,  in  which  all  its  hydrogen  is  replaced  by  a 
metal ; but  the  bibasic  can  yield  two  different  series,  accord- 
ing as  the  metal  replaces  one  or  both  atoms  of  base  ; and 
the  tribasic  can  yield  three  different  series,  according  as  one 
or  two,  or  all  three  of  its  hydrogen  atoms  are  replaced. , 

PHOSPHURETED  HYDROGEN,  PH^  = 34*4, 
may  be  made  by  boiling  phosphorus  in  a strong  solution  of 
lime  or  potash  in  a retort,  Fig.  233,  the  neck  of  which 


dips  beneath  the  surface  of  water,  a few  drops  of  ether  being 
previously  put  into  the  retort.  As  the  bubbles  of  gas  break 
on  the  water,  they  take  fire,  burning  with  a bright  yellow 
light,  and  there  ascends  through  the  air  a ring  of  gray 
smoke,  which  dilates  as  it  rises,  and  exhibits  a curious  rota- 
tory movement  of  its  parts.  This  gas,  also,  may  be  made 
by  bringing  the  phosphuret  of  calcium  in  contact  with  water. 

Phosphureted  hydrogen  is  a colorless  gas,  exhaling  a pe- 
culiar odor,  like  garlic,  and,  when  burning,  produces  phos- 
phoric acid  and  water.  It  exists  under  two  forms  ; 1st. 
Spontaneously  inflammable  ; 2d.  Kot  spontaneously  inflam- 
mable. It  is  said  that  the  first  may  be  changed  into  the 
second  by  small  quantities  of  the  vapor  of  ether,  oil  of  tur- 
pentine, &c.,  and  the  second  into  the  first  by  the  addition 
of  a minute  quantity  of  nitrous  acid. 

How  many  series  of  salts  can  each  class  yield  ? Describe  the  preparation 
of  phosphureted  hydrogen  ? What  are  the  properties  of  phosphureted  hy- 
drogen ? How  may  its  two  forms  be  ponverted  into  each  other  ? 


PREPARATION  OF  CHLORINE. 


235 


CHLORINE.  C/==  35-47. 


Chlorine  is  found  abundantly  in  nature  in  union  with  so- 
dium, forming  common  salt,  a substance  which,  for  the  most 
part,  gives  to  the  sea  water  its  salinity,  and  constitutes  the 
deposits  of  rock  salt.  It  is,  therefore,  an  abundant  sub- 
stance. 

Chlorine  is  best  made  by  the  action  of  hydrochloric  acid 
on  peroxide  of  manganese  : 

MnO^  + 2HCl.,.  = . .,MnCl+2HO+  Cl; 
that  is,  one  atom  of  peroxide  of  manganese  and  two  of  hy- 
drochloric acid  yield  one  atom  of  the  chloride  of  manga- 
nese, two  of  water,  and  one  of  chlorine.  Half  the  chlorine 
is,  therefore,  given  off  as  chlorine  gas,  and  the  other  half 
remains  as  chloride  of  manganese. 

Chlorine  gas  being  very  soluble  in  cold  water,  and  act- 
ing with  great  energy  on  mercury,  it  can 
neither  be  collected  at  the  water  nor  mercu- 
rial trough  ; but,  having  a specific  gravity  of 
2*470,  we  are  able  to  collect  it  by  the  niethod 
of  displacement,  as  shown  in  Fig.  234.  It 
may,  however,  also  be  collected  over  warm 
water  or  a saturated  solution  of  common  salt. 

When  chlorine  is  required  in  a state  of  dryness,  it  may  be 
obtained  by  an  apparatus  like  that  represented  in  Fig.  235. 
a is  the  retort  containing  the  hydrochloric  acid  and  man- 


Fig.  234. 


ganese.  It  is  connected  with  a small  receiver,  h,  which  re- 
tains part  of  the  water  which  the  gas  may  bring  over  ; this. 


In  what  substances  does  chlorine  chiefly  occur  ? How  may  it  be  formed  ? 
What  are  its  properties  ? How  is  it  procured  in  a state  of  drj'ness  ? 


236 


PROPERTIES  OF  CHLORINE, 


again,  is  connected  with  a chloride  of  calcium  tube,  c,  which 
effects  the  perfect  drying  of  the  gas. 

Chlorine  is  a gas  of  a pale  yellowish  green  color.  It  may 
be  liquefied  by  a pressure  of  four  atmospheres.  A taper 
immersed  in  it  burns  for  a few  minutes  with  a dull  red 
flame,  emitting  volumes  of  smoke,  due  to  the  fact  that  the 
Fig.  236.  liydrogen  of  the  flame  continues  to  burn  or  unite 
with  the  chlorine,  forming  hydrochloric  acid  ; but 
the  carbon,  having  little  aflinity  for  chlorine,  is  set 
free  in  an  uncombined  state,  as  lampblack.  Pow- 
dered antimony,  or  thin  brass  leaf,  plunged  in  this 
gas,  becomes  incandescent,  and  burns,  producing  a 
chloride.  A piece  of  phosphorus  immersed  in  it 
takes  fire  at  common  temperatures,  and  burns 
with  a pale  flame.  The  smell  of  chlorine  is  dis- 
agreeable, and  its  effect,  even  in  a diluted  state,  suffocating. 
It  irritates  the  air  passages  of  the  lungs,  producing  hiccough 
and  an  unpleasant  expectoration. 


LECTURE  LII. 

Chlorine,  continued. — Bleaching  Properties.- — Combus- 
tion of  Hydrocarbons. — Disinfecting  Qualities. — Com- 
pounds with  Oxygen.  — Properties  of  Hypochlorous^ 
Chlorous^  and  Chloric  Acids. — Quadrochloride  of  Ni- 
trogen.— Hydrochloric  Acid. — Preparation  in  the  Gas- 
eous and  Liquid  States. 

The  most  valuable  property  of  chlorine  is  its  power  of 
discharging  vegetable  colors,  on  which  is  founded  its  appli- 
Fi  237  bleaching  and  calico  printing. 

■ This  property  may  be  illustrated  in  many  ways.  By 
pouring  a solution  of  litmus  or  indigo  through  a fun- 
j\|  nel,  a.  Fig.  237,  into  a flask,  b,  containing  chlorine 
# decoloration  takes  place  instantly,  or,  if  the 

i hi  color  is  not  completely  discharged,  it  will  be  found, 
in  a short  time,  to  disappear.  The  same  takes  place 
when  a solution  of  chlorine  in  water  is  used. 

What  are  its  relations  in  the  combustion  of  a taper,  and  how  does  it  act 
on  certain  metals  and  phosphorus  ? What  is  its  effects  on  the  animal  sys- 
tem ? Of  the  properties  of  chlorine,  which  is  the  most  valuable  ? How  may 
it  be  illustrated  ? 


PROPERTIES  OF  CHLORINE. 


237 


The  peculiarities  of  chlorine  in  supporting  com-  238. 
bustion  are  remarkable,  when  compared  with  those 
of  oxygen  gas.  A piece  of  paper,  Fig.  238,  dipped 
in  oil  of  turpentine,  takes  fire  in  a moment  at  com- 
mon temperatures  when  placed  in  ajar  of  chlorine, 
and,  as  we  have  seen,  phosphorus  and  several  of 
the  metals  undergo  spontaneous  ignition  in  the  same 
manner.  These  phenomena  depend  on  the  intense 
affinity  which  chlorine  has  for  electro-positive  bod- 
ies, but  it  is  very  remarkable  that  it  seems  to  have  little  dis- 
position to  unite  with  carbon.  As  in  the  burning  of  a taper, 
so  in  this  experiment  with  turpentine,  it  is  the  hydrogen 
which  burns,  and  the  carbon  is  evolved  in  clouds  of  smoke. 

Chlorine  is  also  used  by  physicians  for  the  purpose  of 
destroying  miasmata,  and  the  effluvia  of  sick  rooms  or  oth- 
er places.  It  is  necessary,  from  its  irrespirable  qualities, 
to  disengage  it  slowly  and  with  caution  where  patients  are 
present.  The  chlorides  of  soda  and  lime  are  commonly 
used. 

Free  chlorine  maybe  detected  by  its  smell,  its  bleaching 
action  on  indigo  solution,  and  giving  a white,  curdy  precip- 
itate with  the  nitrate  of  silver.  Its  solution  in  water  is 
readily  made  by  introducing  a small  quantity  of  water  into 
a bottle  full  of  chlorine,  agitating  it,  and  opening  the  mouth 
of  the  bottle  from  time  to  time  under  water  ; the  gas  being 
gradually  absorbed,  the  bottle  becomes  full  of  water,  which, 
of  course,  contains  its  own  volume  of  chlorine.  This  solu- 
tion decomposes  in  the  sunshine,  evolving  oxygen  gas,  the 
water  being  decomposed.  "With  oxygen  chlorine  unites  in 
several  proportions,  producing 

CIO  . . CIO^  . . CZO5  . . CIO,. 

They  are  designated 

Hypochlorous  acid.  I Chloric  acid. 

Chlorous  acid.  | Perchloric  acid. 

HYPOCHLOROUS  ACID.  = 43-483. 

Hypochlorous  acid  may  be  obtained  by  agitating  the  red 
oxide  of  mercury,  suspended  in  water,  with  chlorine.  If  a 
strong  solution  of  it  be  placed  in  an  inverted  tube,  and^ 

What  is  the  cause  of  the  clouds  of  smoke  deposited  when  carburets  of 
hydrogen  bum  in  chlorine  gas  ? For  what  purpose  is  chlorine  used  by  phy- 
sicians? How  may  chlorine  be  detected?  How  may  a solution  of  it  be 
made  ? What  compounds  of  chlorine  and  oxygen  are  known  ? How  is  hy- 
pochlorous acid  made,  and  what  are  its  properties  ? 


238 


ACIDS  OF  CHLORINE. 


pieces  of  diy  nitrate  of  lime  be  added,  the  gas  is  disengaged, 
and  rises  to  the  top  of  the  tube.  It  is  of  a deeper  color 
than  chlorine,  bleaches  powerfully,  and,  by  a slight  eleva- 
tion of  temperature,  explodes,  evolving  two  volumes  of  chlo- 
rine and  one  of  oxygen  gas. 

The  bleaching  compounds  are  compounds  of  chlorides  and 
hypochlorides.  They  are  easily  decomposed  by  acids.  Thus, 
when  chloride  of  lime  is  to  be  used  for  disinfecting  pur- 
poses, it  is  merely  required  to  expose  it  with  water  to  the 
carbonic  acid  of  the  air,  or  to  add  a little  of  it,  from  time 
to  time,  to  a vessel  containing  dilute  sulphuric  acid. 

CHLOROUS  ACID,  0/0^=  67  522, 
may  be  made  by  cautiously  acting  on  small  quantities  of 
chlorate  of  potash  with  sulphuric  acid.  It  is  a yellow  gas, 
which  explodes  furiously  from  very  slight  causes,  the  warmth 
of  the  hand  being  often  sufficient  to  give  rise  to  a violent 
action.  It  contains  two  volumes  of  chlorine  and  four  of  ox- 
ygen, condensed  into  four  volumes.  It  may  be  convenient- 
ly made  by  operating  on  a few  grains  of  the  chlorate  in  a 
Fig.  239.  test  tube.  If  into  a glass,  a.  Fig.  239,  contain- 
ing water,  a small  quantity  of  chlorate  of  pot- 
ash is  placed,  and  upon  it  a few  fragments  of 
phosphorus,  and  sulphuric  acid  be  poured  through 
a funnel,  so  as  to  act  on  the  chlorate,  chlorous 
acid  is  set  free  ; it  communicates  a golden  yel- 
low color  to  the  water,  and  as  each  bubble  pass- 
es by  the  phosphorus  it  sets  it  on  fire,  furnishing  a beauti- 
ful instance  of  combustion  under  water. 

CHLORIC  ACID,  0/05  = 75*535, 

may  be  made  by  decomposing  the  chlorate  of  baryta  by  sul- 
phuric acid,  and  evaporating  the  solution.  It  is  a yellow, 
viscid  acid  : a piece  of  paper  dipped  in  it  is  set  on  fire.  It 
does  not  bleach.  It  forms  salts,  one  of  which,  the  chlorate 
of  potash,  is  of  considerable  importance,  and  is  used  for  the 
preparation  of  oxygen.  A few  grains  of  the  chlorate  of 
potash,  ground  in  a mortar  with  a pinch  of  flowers  of  sul- 
phur, explodes  incessantly  during  the  trituration. 

PERCHLORIC  ACID.  0/0^  = 91*561. 

The  perchlorate  of  potash  forms  along  with  the  chloride 


What  are  the  properties  of  chloric  acid  ? How  may  the  combustion  of 
phosphorus  under  water  be  produced  by  it  ? How  is  chloric  acid  made  ? 


HYDROCHLORIC  ACID. 


239 


of  potassium  when  one  third  of  its  oxygen  is  expelled  from 
chlorate  of  potash;  the  two  salts  may  be  separated*  from 
each  other  by  boiling  in  water,  the  perchlorate  crystallizing  on 
cooling.  From  this  perchloric  acid  may  be  obtained  by  distil- 
lation with  an  equal  weight  of  oil  of  vitriol,  mixed  with  half 
as  much  water.  It  may  be  obtained  in  the  form  of  a white 
crystalline  mass,  very  deliquescent,  and  its  solution  is  some- 
times used  as  a test  for  potash,  with  which  it  gives  a sparing- 
ly soluble  salt.  The  solution  fumes  in  the  air,  has  a specific 
gravity  of  1*65,  and  does  not  possess  bleaching  properties. 

CHLORINE  AND  NITROGEN. 

These  substances  unite,  forming  an  oily  liquid,  when  a 
warm  solution  of  sal  ammoniac  is  exposed  to  chlorine  gas. 
The  resulting  body  is  regarded  as  a quadrichloride  of  nitro- 
gen (JVCIJ.  By  its  violent  explosions,  several  eminent 
chemists  have  been  seriously  injured.  The  mere  contact 
of  oily  matter  produces  a detonation. 

CHLORINE  AND  HYDROGEN. 

HYDROCHLORIC  ACID.  = 36*47. 

This  acid,  called  also  muriatic  acid,  is  easily  prepared  by 
placing  in  a flask  six  parts  of  common  salt  and  ten  parts 
by  weight  of  oil  of  vitriol,  mixed  with  four  of  water,  the 
mixture  being  sufiered  to  cool  before  it  is  introduced.  On 
heating  the  mixture,  hydrochloric  acid  is  evolved,  which 
passes  along  a bent  tube  into  a bottle  containing  six  parts 
(by  weight)  of  water.  The  end  of  the  tube  dips  but  a very 
short  distance  beneath  the  surface  of  this  water,  so  that  if 
the  liquid  should  rise  it  may  be  received  into  a ball  blown 
upon  the  tube,  and  the  extremity  of  the  tube  becoming  uncov- 
ered, atmospheric  air  may  pass  into  the  interior  of  the  flask. 
At  the  close  of  the  process,  the  liquid  in  the  bottle,  which 
should  be  constantly  surrounded  by  ice  water  in  a small 
tank,  more  than  doubles  its  volume,  and  is  a pure  solution 
of  hydrochloric  acid.  The  action  is 

Na  Cl  + 2{HO,  80^)...  = .. . HCl  + (iVaO,  HO,  2SO,) ; 
that  is,  one  atom  of  chloride  of  sodium  and  two  of  sulphuric 
acid  yield  one  atom  of  hydrochloric  acid  and  one  of  the  bi- 
sulphate of  soda. 

How  is  perchloric  acid  prepared,  and  for  what  purpose  is  it  used  ? What 
made  ? chloride  of  nitrogen  ? How  is  hydrochloric  acid 


240 


HYDROCHLORIC  ACID. 


From  the  liquid  thus  produced,  or  from  the  commercial 
muriatic  acid,  by  heating  in  a flask,  pure  hydrochloric  acid 
gas  may  be  obtained ; it  may  also  be  less  advantageously 
procured  by  the  direct  action  of  strong  oil  of  vitriol  on  com- 
mon salt,  the  reaction  in  this  case  being 

NaCl  -+•  HO,  SO^  . IICl  + NaO,  SO^, 

Pure  hydrochloric  acid  is  a transparent,  colorless  gas, 
possessing  powerful  acid  qualities,  very  absorbable  by  wa- 
ter, which  liquid  takes  up  several  hundred  times  its  own 
volume  of  the  gas  ; it  fumes  in  moist  air,  and 
has  a pungent  odor.  If  a dry  Florence  flask 
{Fig.  240)  be  filled  with  it  by  the  process  of 
displacement,  and  the  mouth  of  it  opened  un- 
der the  surface  of  cold  water,  the  water  rushes 
up  into  the  flask,  absorbing  the  gas  with  great 
violence.  The  specific  gravity  of  hydrochloric 
acid  is  1-284.  It  contains  equal  volumes  of  its  constituents, 
united  without  condensation. 


LECTURE  LIII. 

Chlorine,  co’^^mv'ED.— Production  of  Hydrochloric  Acid 
ly  Light. — Action  of  Hydrochloric  Acid  on  Metallic 
Protoxides. — Muriatic  Acid  Solution.  — Detection  of 
Hydrochloric  Acid. — Nitro-muriaiic  Iodine. — 

Sources  of. — Preparations  and  Properties. — Tests  for 
Iodine. — Its  Action  on  Starch. — Hy dr  iodic  Acid. — 
" Oxygen  Compounds  of  Iodine. 

Pure  hydrochloric  acid  gas  is  also  obtained  when  a mix- 
ture of  chlorine  and  hydrogen,  in  equal  proportions,  is  ex- 
posed to  the  light.  In  the  dark  these  gases  appear  to  have 
no  disposition  to  unite,  but  if  they  be  placed  in  a flask  cov- 
ered over  with  a wire  screen,  and  a beam  of  the  sunlight 
reflected  upon  them  from  a looking-glass,  a violent  explosion 
ensues,  and  hydrochloric  acid  is  formed. 

I have  found  that,  in  this  remarkable  experiment,  the 

How  may  the  gas  be  procured  ? What  are  the  properties  of  hydrochloric 
acid  gas  1 How  may  its  affinity  for  water  be  proved  ? What  is  its  con- 
stitution ? What  is  the  action  of  sunlight  on  a mixture  of  chlorine  and  hy- 
drogen ? 


Fig.  240. 


PROPERTIES  OP  HYDROCHLORIC  ACID.  241 

action  is  chiefly  duo  to  the  chlorine,  which,  from  being  in 
a passive,  assumes  an  active  state  by  exposure  to  rays  of 
an  indigo  color.  It  may  be  thrown  into  the  same  condition 
in  many  other  ways ; lor  example,  by  the  contact  of  spongy 
platina.  Moreover,  when  chlorine  by  itself  has  been  ex- 
posed to  the  sun,  it  gains  the  quality  of  uniting  more  easily 
with  hydrogen  than  chlorine  which  has  been  made  and 
kept  in  the  dark. 

When  hydrochloric  acid  is  brought  in  contact  with  me- 
tallic oxides,  decomposition  of  both  ensues,  and  metallic  chlo- 
rides are  formed,  thus : 

MO  -f  HCl  MCI  4-  HO; 

or,  M2O3  + 2>{HCl)  .M^Cl^  + 3HO; 

that  is,  one  atom  of  a metallic  protoxide  with  one  atom  of 
hydrochloric  acid  yields  one  atom  of  a protochloride  of  the 
metal  and  one  of  water.  But,  in  the  case  of  a sesquioxide, 
one  atom  of  it  with  three  of  hydrochloric  acid  yield  one  atom 
of  the  metallic  sesquichloride  and  three  of  water. 

The  constitution  of  hydrochloric  acidj  and  its  ac- 
tion  on  metallic  oxides,  may  be  strikingly  illustrated 
by  taking  a flask,  b {Fig.  241),  filled  with  it,  in  a 
perfectly  dry  state,  and  allowing  the  peroxide  of 
mercury,  in  fine  powder,  to  fall  through  it.  The  bi- 
chloride of  mercury,  corrosive  sublimate,  instantly 
forms,  and  drops  of  water  make  their  appearance  on 
the  sides  of  the  flask. 

It  is  under  the  form  of  a solution  in  water,  as  liquid  mu- 
riatic acid,  or  spirit  of  salt,  that  hydrochloric  acid  is  chiefly 
used.  The  mode  of  obtaining  it  has  been  described  in  the 
last  Lecture.  This  liquid,  when  concentrated,  has  a speci- 
fic gravity  of  1’21,  and  contains  42  per  cent,  of  acid.  It 
smokes  in  the  air,  and  reddens  blue  litmus  powerfully.  The 
commercial  acid  is  usually  .of  a ^^ellow  color ; it  contains 
chloride  of  iron,  derived  from  the  iron  vessels  from  which  it 
is  distilled.  It  also  often  contains  sulphuric  acid,  chlorine, 
sulphurous  acid,  tin,  or  arsenic,  and  is,  therefore,  best  pre- 
pared by  the  process  described,  which  yields  it  in  perfect 
pufity. 

Hydrochloric  acid  may  be  detected  by  yielding,  when  in 

To  which  of  these  bodies  is  this  action  due  ? What  is  the  action  of  hy- 
drochloric acid  on  metallic  oxides  ? What  arc  the  products  of  the  action 
of  hydrochloric  acid  on  peroxide  of  mercury  ? What  arc  thp  properties  of 
liquid  muriatic  acid  ? What  are  its  impurities  ? 

L 


242 


NITRO-MURIATIC  ACID. 


Fig.  242.  ^ state  with  ammonia,  dense  white  clouds  of 

sal  ammoniac.  If  two  glasses,  one  filled  with 
this  acid,  and  the  other  with  ammonia,  be  brought 
near  each  other,  a white  cloud  forms  between 
them.  A glass  rod,  a {Fig.  243),  dipped  in  am- 
monia, may  be  used  for  the  same  pur-  Fig.  243. 
pose.  With  nitrate  of  silver,  hydro- 
chloric acid  yields  a white  chloride  of  silver, 
which  turns  black  in  the  light,  being  the  same 
precipitate  given  under  the  same  circumstances 
by  free  chlorine.  From  this  latter  substance  it 
may  be  distinguished  by  litmus  water,  which  is 
bleached  by  chlorine,  and  reddened  by  hydrochloric  acid. 

Nitro-muriatic  acid,  or  aqua  regia,  is  formed  by  adding 
to  hydrochloric  acid  one  half  or  a third  of  its  volume  of  ni- 
tric acid.  The  nitric  acid,  furnishing  oxygen  to  the  hydro- 
chloric acid,  forms  water,  and  chlorine,  with  nitrous  acid, 
is  set  free  in  the  solution.  Aqua  regia  is  used  as  a solvent 
for  platina  and  gold,  a result  which  may  be  illustrated  by 
placing  a sheet  of  gold  leaf  in  the  mixture. 

IODINE.  J=126'57.  • 

Iodine  chiefly  occurs  in  the  products  of  the  sea,  being 
found  in  sea- weed ^ sponge,  &c. ; and  also  in  certain  brine 
springs,  and  in  some  ores  of  silver  and  zinc. 

It  may  be  obtained  by  lixiviating  the  ashes  of  sea-weeds, 
and  evaporating  the  solution  until  no  more  crystals  are  de- 
posited. The  residual  liquor  is  then  acted  upon  by  sulphuric 
acid,  and  subsequently  heated  with  peroxide  of  manganese, 
in  a leaden  retort,  ah  c {Fig.  244,  page  243),  the  iodine 
distills  over  into  the  receivers,  d. 

It  is  a solid  substance,  of  a deep  blue  or  black  appear- 
ance, with  a semi-metallic  lustre,  communicates  to  the  skin 
a fugitive  yellow  stain,  and  exhales  an  odor  like  that  of  sea 
beaches.  It  crystallizes  in  rhomboidal  plates,  is  brittle, 
and  has  a specific  gravity  of  4-948.  At  225^  it  melts,  and 
boils  at  347^,  exhaling,  even  at  moderate  temperatures, 
a splendid  purple  vapor,  from  which  its  name  is  derived. 
The  specific  gravity  of  this  vapor  is  8*707 ; it  is,  therefore, 
one  of  the  heaviest  gaseous  bodies  known. 

- How  may  hydrochloric  acid  be  detected?  What  is  the  preparation  and 
property  of  nitro-muriatic  acid?  From  what  source  is  iodine  procured? 
What  is  the  method  of  its  preparation?  What  is  its  appearance?  What 
is  the  color  of  its  vapor  ? From  what  circumstance  is  its  name  derived  ? 


IODINE. 


243 


Fig.  245. 


Fig.  246. 


Iodine  supports  combustion  much  in  the  same 
manner  as  chlorine.  A jar,  a {Fig.  245),  con- 
taining a few  grains  of  it,  placed  in  a small  sand 
bath,  b,  and  warmed  by  a spirit  lamp,  c,  may  be 
easily  filled  with  its  dense  vapor,  the  atmos- 
pheric air  floating  out  before  it.  In  this  vapor, 
if  a lighted  taper  is  plunged,  it  exhibits  a retard- 
ed combustion  ; but  a piece  of  phosphorus,  intro- 
duced on  a spoon,  takes  fire  and  burns.  In  the 
same  manner,  if  a quantity  of  iodine  be  placed  in  a small 
capsule,  and  upon  it  a fragment  of  dry  phos- 
phorus {Fig.  246),  spontaneous  ignition  en- 
sues, Avith  the  evolution  of  phosphoric  acid, 
and  the  vapor  of  iodine,  iodide  of  phosphorus, 
remaining  in  the  capsule. 

In  Avater,  iodine  is  but  slightly  soluble, 
that  liquid  taking  up 
weight,  and  assuming  a brown  color.  Al- 
cohol dissolves  it  freely,  forming  tincture  of 
iodine.  In  solutions  of  the  iodides,  iodine  may  be  dissolved. 

With  many  substances  iodine  gives  characteristic  reac- 
tions. The  iodide  of  potassium,  with  the  acetate  of  lead, 
yields  a golden  yellow  precipitate  ; with  the  bichloride  of 


What  are  its  relations  as  resDects  combustion  1 Is  it  soluble  in  water 
and  alcohol  ? ^ 


244 


IIYDIUOCIC  ACID. 


mercury,  a fine  scarlet-colored  biniodide.  This  substance 
; possesses  the  singular  quality  that,  if  dried  and  sublimed  in 
a tube,  it  yields  crystals  of  a brilliant  yellow  aspect,  which 
become  red  on  being  simply  touched  with  a hard  body. 
With  a solution  of  starch,  free  iodine  yields  a deep  blue  color, 
the  solution  becoming  colorless  if  heated,  but  the  blue  color 
returning  on  cooling,  provided  the  temperature  has  not  been 
carried  to  the  boiling  point.  If  a potato  be  cut  in  two,  and 
a little  tincture  of  iodine  poured  on  the  surface,  innumera- 
ble blue  specks  make  their  appearance,  each  corresponding 
to  the  position  of  a granule  of  starch.  Starch  and  free 
iodine  will,  therefore,  mutually  detect  the  presence  of  each 
other. 

HYDRIODIC  ACID.  7/1=  127*57. 

Hydriodic  acid  gas  may  be  obtained  by  dissolving  in  a so- 
lution of  iodide  of  potassium  as  much  iodine  as  it  will  hold, 
adding  small  pieces  of  phosphorus,  and  warming  the  mix- 
ture. A colorless  transparent  gas  is  evolved,  which  fumes 
in  the  air,  and  may  be  collected  over  mercury.  Its  specific 
gravity  is  4*384.  It  has  the  general  relations  of  hydro- 
chloric acid,  and,  like  it,  is  very  soluble  in  water. 

Fig.  247.  A solution  of  hydriodic  acid  in  water  may  be 
made  by  passing  a stream  of  sulphureted  hydro- 
gen from  a flask,  a {Fig.  247),  through  water, 
bi  in  which  iodine  is  suspended.  The  acid  forms, 
and  sulphur  is  deposited  : 

1+  HS...=z  HI. 

With  nitrate  of  silver  this  acid  yields  a pale  yellow  pre- 
cipitate, the  iodide  of  silver.  This  is  the  substance  which 
forms  the  basis  of  the  remarkable  compound  used  in  the 
Daguerreotype.  In  that  case  it  is  formed  by  holding  a 
plate  of  pure  polished  silver  in  the  vapor  of  iodine ; the 
plate  tarnishes  and  turns  yellow,  and,  if  set  in  the  sunshine, 
turns  promptly  of  a deep  olive  black. 

Iodine  yields  two  oxygen  acids,  iodic  {10^  and  periodic 
acid  (/O7).  With  nitrogen,  also,  it  gives  character- 
ized, like  the  analogous  compound  of  chlorine,  by  the  facility 
with  which  it  explodes. 


How  may  it  be  detected  ? In  what  manner  is  hydriodic  acid  made  ? 
What  is  the  simplest  method  of  obtaining  a solution  of  it  ? What  is  the 
precipitate  it  yields  with  nitrate  of  silver?  What  are  the  oxygen  com- 
pounds of  iodine  ? 


BROMINE. 


245 


LECTURE  LIV. 

Bromine. — Fluorine. — Bromine. — Sources  of. — Proper^ 
ties. — Compounds  of. — Fluorine. — Hydrofluoric  Acid. 
— Its  Properties  and  Action  on  Glass. — Carbon. — Al- 
lotropic  Forms  of. — Preparation  of  some  of  those  Forms. 
— Diamond.  — Oxygen  Compounds  of  Carbon.  — Car- 
bonic Oxide. 


BROMINE.  Br  = 78-39. 

Bromine  occurs  in  sea  water,  and  also,  to  a more  consid- 
erable extent,  in  certain  brine  springs  both  in  America  and 
Europe.  From  these  it  may  be  obtained  by  evaporating 
the  water  until  the  salt  solution  is  concentrated,  and  after 
the  chloride  of  sodium  has  crystallized  from  the  liquor,  pass- 
ing through  it  a current  of  chlorine  gas,  the  solution  turning 
yellow  as  the  bromine  is  set  free.  It  is  next  agitated  with 
sulphuric  ether,  which  carries  to  the  surface  all  the  bro- 
mine. This  is  then  acted  on  by  potash,  which  gives  a mix- 
ture of  bromate  of  potash  and  bromide  of  potassium.  On 
ignition,  oxygen  is  expelled,  and  the  whole  converted  into 
the  latter  salt,  from  which  the  bromine  may  be  distilled  by 
the  aid  of  peroxide  of  manganese  and  sulphuric  acid. 

It  is  a liquid  of  a deep  blood-red  appearance,  solidifying 
at — 40°  F.,  and  boiling  at  113°  F.  Its  specific  gravity  is 
2-99.  It  exhales  an  orange  vapor,  and  is  commonly  kept 
beneath  the  surface  of  water.  Its  smell  is  very  disagree- 
able, a circumstance  from  which  its  name  is  derived.  Like 
chlorine,  it  bleaches,  and  in  all  its  relations  possesses  a gen- 
eral resemblance  to  that  substance.  A lighted  taper  burns 
for  a short  time  in  its  vapor  with  a greenish  flame.  Phos- 
phorus burns  spontaneously  in  it. 

Bromine  yields  a hydrogen  acid  {HBr),  hydrobromic  acid, 
and  with  oxygen,  bromic  acid  [BrO^.  In  their  general 
properties  these  bodies  resemble  the  corresponding  com- 
pounds of  chlorine.  The  bromide  of  silver  is  much  more 
sensitive  to  light  than  either  the  chloride  or  iodide. 

FLUORINE,  E=  18-74, 

is  found  in  combination  with  calcium,  as  the  fluoride  of  cal- 


From  what  source  is  bromine  obtained  ? What  are  the  properties  of  bro 
mine,  and  to  what  bodies  has  it  a close  analogy  ? 


246 


CARBON. 


cium,  or  fluor  spar.  It  occurs  also  in  the  topaz  and  other 
minerals.  In  the  enamel  of  teeth  and  in  bones  it  has  been 
detected,  especially  in  fossil  bones,  which  sometimes  contain 
as  much  as  ten  per  cent,  of  fluoride  of  calcium. 

The  special  properties  of  fluorine  are  as  yet  unknown,  for 
it  has  not  been  isolated.  Various  attempts  have  been  made 
at  different  times,  but  without  satisfactory  results.  It  pos- 
sesses an  intense  affinity  for  electro-positive  bodies,  and  gives 
rise  to  a series  of  compounds  resembling  those  of  chlorine, 
iodine,  &c.  It  does  not  unite  with  oxygen. 

HYDROFLUORIC  ACID.  HF=1974. 

This  energetic  acid  may  be  obtained  by  decomposing  fluo- 
ride of  calcium  by  sulphuric  acid  in  a vessel  of  platina  or 
lead,  the  vapors  being  conducted  into  a metallic  receiver 
kept  at  a low  temperature.  The  action  is 

CaF+HO,  SO^.. . = . . . CaO,  SO^  + HF. 

It  is  a smoking  liquid,  which  acts  powerfully  on  the  skin, 
boils  at  a temperature  of  a little  above  60^  F.,  and  possesses 
the  remarkable  quality  of  corroding  glass. 

If  a piece  of  glass  be  coated  over  with  a thin  film  of 
bees’  wax,  and  letters  or  other  marks  made  through  the  wax 
to  the  glass  with  a pointed  implement,  on  setting  it  over  a 
vessel  of  lead  or  tin  in  which,  from  a mixture  of  fluor  spar 
and  sulphuric  acid,  hydrofluoric  acid  is  escaping  in  vapor,  the 
glass  is  deeply  etched  on  all  those  parts  which  have  been 
uncovered,  as  is  seen  when  the  wax  is  removed.  Liquid 
hydrofluoric  acid  may  be  employed  for  the  same  purpose, 
but  the  letters  are  not  so  visible  as  when  the  vapor  is  used. 

CARBON.  0 = 604. 

This,  which  is  one  of  the  most  interesting  and  important 
of  the  elementary  bodies,  occurs  under  many  different  natu- 
ral forms.  It  is  an  essential  ingredient  in  the  structure  of 
all  animal  and  vegetable  beings ; it  is  found  in  various  states 
in  the  air,  the  sea,  and  the  crust  of  the  earth. 

The  striking  peculiarity  of  carbon,  which  at  once  arrests 
our  attention,  is  the  different  allotropic  conditions  under 
which  it  is  presented.  This  substance  may  be  said  to  yield 
in  itself  a whole  group  of  elementary  bodies.  Among  these 

Are  the  special  properties  of  fluorine  known  ? How  is  hydrofluoric  acid 
made  ? What  remarkable  quality  does  it  possess  ? From  what  sources 
may  carbon  bo  procured  T What  is  its  most  striking  property  ? 


FORMS  OF  CARBON. 


247 


might  he  enumerated,  (1.)  Diamond,  which  crystallizes  in 
octahedrons,  is  transparent,  incombustible,  except  in  oxygen 
gas,  and  the  hardest  body  known ; hence  its  use  in  cutting 
glass.  (2.)  Gas-carbon,  which,  unlike  diamond,  is  a good 
conductor  of  electricity,  and  is  opaque.  (3.)  The  various 
forms  of  charcoal,  anthracite  coal,  and  coke.  (4.)  Plumba- 
go, which  has  a metallic  lustre,  is  opaque,  and  so  soft  and 
unctuous  that  it  is  used  to  relieve  the  friction  of  machinery. 
(5.)  Lampblack,  a powerful  absorbent  of  light  and  heat, 
and  possessing  such  strong  affinity  for  oxygen  that  it  can 
take  fire  spontaneously  in  the  air. 

Other  forms  of  carbon  might  be  cited  ; these,  however, 
are  enough  to  establish  the  fact  that  this  single  body  fur- 
nishes varieties  which  differ  more  strikingly  from  each  other 
than  many  different  metallic  bodies. 

Charcoal  is  made  by  the  ignition  of  wood  in  close  ves- 
sels, the  volatile  materials  being  dissipated  and  the 
carbon  left.  The  nature  of  the  process  may  be  illus-  J Ij 
trated  by  taking  a slip  of  wood,  d,  Fig.  248,  and  plac-  jM 
ing  its  burning  extremity  in  a test  tube,  a.  This  re- 
tards  the  access  of  the  surrounding  air,  and,  as  the 
combustion  proceeds,  a cylinder  of  charcoal  is  left. 

Tig.  249.  Lampblack,  is  formed  on 

a similar  principle.  In  the 
iron  pot,  a,  Fig.  249,  some 
pitch  or  tar  is  made  to  boil, 
a small  quantity  of  air  being  ad- 
mitted through  apertures  in  the 
brickwork.  Imperfect  combustion 
takes  place,  the  hydrogen  alone 
burning,  the  carbon  being  carried 
as  a dense  cloud  of  smoke  into  the 
chamber  ^ c by  the  draft.  In  this 
there  is  a hood,  or  cone,  of  coarse 
cloth,  which  may  be  raised  or 
lowered  by  a pulley.  The  sides  of  the  chamber  are  covered 
with  leather,  and  on  these  the  lampblack  collects. 

Diamond  is  the  purest  form  of  carbon.  Its  specific  grav- 
ity is  3*5  : it  exhibits  a high  refractive  and  dispersive  action 
upon  light.  Charcoal  possesses,  in  consequence  of  its  por- 
ous structure,  the  quality  of  absorbing  many  times  its  own 

Mention  some  of  its  allotropic  forms.  How  are  charcoal  and  lampblack 
made  ? What  are  the  properties  of  diamond  ? 


248 


CARBONrC  OXIBE. 


volume  of  different  gases.  Ivory  black,  which  is  made  by 
the  ignition  of  bones  in  close  vessels,  has  the  valuable  qual- 
ity of  removing  organic  coloring  matters  from  their  solu- 
tions : a property  which  may  be  shown  by  filtering  a solu- 
tion of  indigo  through  it.  In  all  its  forms,  carbon  seems  to 
be  infusible,  but  when  burned  in  air  or  an  excess  of  oxygen, 
they  all  give  rise  to  carbonic  acid  gas.  It  combines  direct- 
ly with  several  of  the  metals,  yielding  carburets.  With 
oxygen  it  gives  two  compounds, 

CO 

designated  respectively  as  carbonic  oxide  and  carbonic  acid. 

CARBONIC  OXIDE,  CO  = 14  053, 
is  produced  when  carbon  is  burned  in  a limited  supply  of 
'oxygen,  or  when  carbonic  acid  is  passed  over  red-hot  iron 
or  over  red-hot  carbon.  In  these  cases  the  actions  are  : 
CO2+  C ...rzr...2(CO). 

CO2  + Fe...  = ...CO  + FeO. 

In  the  first  the  carbonic  acid  unites  with  one  atom  of 
carbon,  and  yields  two  of  carbonic  oxide  ; in  the  second, 
it  loses  one  atom  of  oxygen  to  the  iron  and  yields  one  of 
Ei^.250.  carbonic  oxide.  It  may  also  be  pre- 

pared by  heating  oxalic  acid  with  oil 
of  vitriol  in  a flask,  a.  Fig.  250,  the 
decomposition  giving  equal  volumes  of 
carbonic  acid  and  carbonic  oxide,  as  is 
explained  under  oxalic  acid.  The  acid 
may  be  separated  by  passing  the  mix- 
ture through  a bottle,  5,  containing  potash  water,  and  the 
Fig.25i.  oxide  collected  over  water.  But  the  best 
process  for  procuring  it  is  to  heat  one  part 
of  prussiate  of  potash  with  ten  of  oil  of 
vitriol  in  a retort : the  carbonic  oxide 
comes  over  in  a state  of  purity. 

As  obtained  by  any  of  these  processes, 
it  is  a colorless  gas,  which  may  be  kept 
over  water,  in  which  it  is  only  sparingly 
soluble.  It  is  without  odor,  and  is  irre- 
spirable.  A j et  of  it  burns  in  the  air  with 

What  are  the  properties  of  ivory  black?  What  are  the  oxygen  com- 
pounds of  carbon  ? What  is  the  action  of  carbon  and  of  metallic  iron  on 
carbonic  acid  at  a red  heat  ? How  is  carbonic  oxide  produced  from  oxalic 
acid  ? From  what  other  substance  may  it  be  procured  ? 


CARBONIC  ACID. 


249 


a beautiful  blue  flame,  combining  with  oxygen  and  yielding 
carbonic  acid.  Its  specific  gravity  is  O’ 97 22  : it  has  never 
been  liquefied.  It  is  the  combustion  of  this  gas  which  pro- 
duces the  blue  flame  often  seen  in  a coal  fire.  Carbonic 
oxide  is  a compound  radical,  giving  origin  to  a series  of 
bodies. 


LECTURE  LV. 

Carbonic  Acid. — Methods  of  Preparation  hy  Decomposi- 
tion and  Combustion, — General  Properties,  and  Rela- 
tion to  Combustion  and  Respiration. — Its  Solution  in 
Water. — Exists  in  the  Breath. — Its  Liquid  and  Solid 
Forms. — Light  Carbureted  Hydrogen. — Marsh  Gas. 
— Natural  and  Artificial  Production. — Olefiant  Gas. 
— Action  ivith  Chlorine. 

CARBONIC  ACID.  C02  = 23-066. 

Carbonic  acid  is  commonly  prepared  by  the  action  of 
dilute  hydrochloric  acid  on  chalk,  or  any  carbonate  of  lime, 
the  action  being 

CaO,  CO.,  + HCl  CaCl,  HO  + CO,\ 

that  is  one  atom  of  carbonate  of  lime  and  one  252. 

of  hydrochloric  acid  yield  one  atom  of  chloride 
of  calcium  and  one  of  water,  and  one  atom  of 
carbonic  acid  gas  is  set  free.  The  process 
may  be  conducted  in  a flask,  as  in  the  figure, 
the  gas  being  evolved  so  rapidly  that  it  may 
be  collected  over  water,  though  that  liquid  ab- 
sorbs it  very  freely. 

Carbonic  acid  is  abundantly  formed  in  many  processes. 
It  is  the  result  of  the  complete  combustion  of  carbonaceous 
bodies,  is  evolved  during  the  respiration  of  animals,  and  in 
alcoholic  fermentation.  It  is  the  fixed  air  of  the  older 
chemists. 

It  is  a colorless  and  transparent  gas  at  common  temper- 
atures, with  a faint  smell  and  slightly  acid  taste.  It  is  ir- 


What  are  the  properties  of  carbonic  acid  gas  1 How  is  this  gas  made  ? 
Under  what  circumstances  is  carbonic  acid  formed  during  combustion  ? In 
what  other  processes  does  it  appear? 

L 2 


250 


CARBONIC  ACID. 


respirable,  and  acts  in  a diluted  state  as  a narcotic  poison ; 
even  air,  containing  one  tenth  of  its  volume  of  this  gas,  pro- 
duces a marked  effect.  Its  specific  gravity 
is  1-527,  and  it  may,  therefore,  be  collected 
by  displacement  {Fig.  253).  For  the  same 
reason,  it  collects  in  the  bottom  of  wells  and 
pits,  and  often  suffocates  workmen  who  de- 
scend into  such  places.  It  does  not  support 
combustion ; a lighted  taper  lowered  into  a 
jar  partly  filled  with  it  is  extinguished  the  moment  it 
reaches  the  gas.  It  may  be  poured  from  one  vessel  to  an- 
other ; and  if  a jar  of  it  is  poured  upon  the  flame  of  a can- 
dle, the  light  is  at  once  extinguished.  Its  density  and  other 
qualities  may  be  well  illustrated  when  it  is  formed  by  the 
action  of  fuming  nitric  acid  on  carbonate  of  ammonia,  a 
smoky  cloud  marking  its  position  and  movements. 

Carbonic  acid  reddens  litmus  water,  but  the  blue  color 
Fig.  254.  restored  on  boiling,  the  acid  being  Fig.  255. 
n driven  off  by  the  heat.  It  is  soluble 

I:  in  water,  which,  under  increased 

Ij  pressure,  takes  up  several  times  its 

II  volume  of  it,  constituting  the  soda 
II  water  of  the  shops.  Its  solubility 
may  be  established  by  agitating  it 
with  water  in  Hope’s  eudiometer. 

Fig.  254,  or  by  passing  it  through 
Nooth’s  soda-water  machine.  Fig.  255. 

A common  test  for  the  presence  of  car- 
bonic acid  in  wells  is  to  lower  a lighted 
candle,  and  if  its  flame  be  extinguished,  it 
is  inferred  that  the  gas  is  present ; but  it 
does  not  follow  that  a man  may  safely  descend  into  such 
places  though  a candle  will  continue  to  burn. 

If,  through  a tube,  the  breath  be  made  to  pass  into  lime- 
water,  a deposit  of  carbonate  of  lime  renders  the  water 
milky ; or,  if  the  breath  be  conducted  through  litmus  water, 
the  color  changes  to  red  ; the  air  thus  expired  from  the 
lungs  contains  three  or  four  per  cent,  of  carbonic  acid. 

Under  a pessure  of  thirty-six  atmospheres,  carbonic  acid 
condenses  into  a liquid  characterized  by  the  extraordinary 

What  are  the  properties  of  carbonic  acid  ? What  are  its  relations  to  com- 
bustion? What  is  its  specific  gravity?  What  is  soda  water?  How  may- 
carbonic  acid  be  detected  ? How  can  its  existence  in  the  breath  be  proved  ? 


Fig.  2.53. 


CARBON  AND  HYDROGEN. 


251 


quality  that  it  is  four  times  more  expansible  by  heat  than 
even  atmospheric  air.  This  liquid,  when  allowed  to  escape 
through  a jet,  evaporates  so  rapidly,  and  produces  so  much 
cold,  that  a portion  of  it  instantly  solidifies.  Solid  carbonic 
acid  is  a substance  not  unlike  snow;  mixed  with  alcohol 
or  ether,  it  produces  a degree  of  cold  equal  to  — 180°  Fahr. 

Although  carbonic  acid  has  the  name  of  an  acid,  it  pos- 
sesses the  properties  indicated  by  that  term  in  a feeble  de- 
gree. The  gas  contains  its  own  volume  of  oxygen.  The 
common  test  for  its  presence  is  lime-water,  which  is  render- 
ed turbid  by  it. 

CARBON  AND  HYDROGEN. 

These  substances  unite,  producing  many  compounds,  some 
of  which  are  solid,  some  liquid,  and  others  gaseous.  They 
are,  of  course,  all  combustible  bodies,  and  the  description  of 
nearly  all  of  them  belongs  to  organic  chemistry. 

LIGHT  CARBURETED  HYDROGEN,  CH2  = 8 04, 
occurs  abundantly  in  coal  mines,  and  forms  with  their  at- 
mospheric air  explosive  mixtures ; it  is  also  found  during  the 
putrefaction  of  vegetable  matter  under  water ; on  stirring 
the  mud  of  ponds,  bubbles  of  this  gas  escape ; hence  the 
name  marsh  gas.  It  may  be  obtained  artificially  by  heat- 
ing acetate  of  potash  with  hydrate  of  baryta. 

(7TO)  + + {BaC.  ^O)  , {KO,  CO,)  + 

{BaO,  CO,)  + 2Cir,; 

that  is,  one  atom  of  acetate  of  potash  with  one  of  hydrate 
of  baryta  yield  one  of  carbonate  of  potash,  one  of  carbonate 
of  baryta,  and  two  of  light  carbureted  hydrogen  gas,  the 
acetic  acid  being  decomposed,  by  the  aid  of  water,  into  car- 
bonic acid  and  marsh  gas.  It  is  a colorless  gas,  burns  with 
a yellow  flame,  producing  water  and  carbonic  acid.  Its 
specific  gravity  is  0*555,  forms  explosive  mixtures  with  air, 
and  is  the  fire-damp  of  coal  mines.  The  choke-damp,  which 
exists  in  mines  after  an  explosion,  is  carbonic  acid  gas,  orig- 
inating from  the  combustion.  This  gas  is  decomposed  by 
chlorine  in  the  light,  but  not  in  darkness. 

What  are  the  properties  of  liquid  and  solid  carbonic  acid  t What  is  the 
test  for  it  ? How  may  light  carbureted  hydrogen  be  made  ? Where  is  it 
found  naturally  ? Of  what  does  the  explosive  gas  of  coal  mines  consist  ? 


252 


OLEFIANT  GAS. 


OLEFIANT  GAS. 

Olefiant  gas  may  be  made  by  heating  one  part  of  alcohol 


Fig.  256. 


with  four  of  sulphuric  acid  in  a flask,  a, 
Fig.  256.  The  vapor  of  ether  which 
comes  over  with  it  may  be  removed  by 
causing  the  gas  to  pass  through  a small 
bottle,  5,  containing  sulphuric  acid,  be- 
fore being  collected  at  the  trough.  It 
' may  also  be  obtained  by  an  apparatus 
such  as  Fig.  257,  in  which  b is  the  flask  containing  alcohol 


Fig.  258. 


and  sulphuric  acid,  and  a an  interposed  globe  to  receive  the 
ether,  oil  of  wine,  and  water,  which  distill  over. 

Olefiant  gas  is  transparent  and  color- 
less ; burns  with  a beautiful  flame  {Fig. 
258) ; forms  an  explosive  mixture  with 
oxygen,  giving  rise  by  its  combustion  to 
carbonic  acid  and  water.  If  mixed  with 
an  equal  volume  of  chlorine,  the  gases 

[ condense  into  an  oily  liquid,  from  which 

olefiant  gas  has  received  its  name.  With 
twice  its  volume  of  chlorine,  if  it  be  set 
on  fire,  hydrochloric  acid  is  formed,  and 
carbon  is  deposited  as  a dense  black  smoke. 

Olefiant  gas  also  exists  as  one  of  the  chief  ingredients  in 
the  gas  employed  for  illuminating  cities. 

; How  is  olefiant  gas  prepared  ? What  are  the  products  of  combustion  of 
olefiant  gas  ? What  is  the  action  of  chlorine  on  it  ? From  what  has  it  de- 
xived  its  name  ? 


CYANOGEN* 


253 


LECTURE  LVL 

Cyanogen. — Modes  of  Preparation. — Liquefaction. — An 
Electro-negative  Compound  Radical. — Bisulphuret  of 
Carbon. — Boron. — Boracic  Acid. — Terfluoride  of  Bo- 
ron.— Silicon. — Silicic  Acid. — Fluoride  of  Silicon. — 
Compounds  of  Hydrogen  and  Nitrogen.  — Amidogen. 
— Ammonia. — Ammonium. — Theory  of  Berzelius. 

CYANOGEN,  Cy..OR  BICARBURET  OF  NITROGEN.  C^N=26.23. 

Carbon  unites  with  nitrogen,  forming  a bicarburet,  when 
these  substances  are  in  the  nascent  state  and  in  presence 
of  a base.  It  may  be  obtained  very  easily  by  exposing  the 
cyanide  of  mercury  to  heat,  or  by  heating  a mixture  of  six 
parts  of  ferrocyanide  of  potassium  and  nine  of  corrosive  sub- 
limate. 

It  is  a colorless  gas,  having  a peculiar  odor.  It  burns 
with  a beautiful  purple  flame,  dissolves  readily  in  water, 
and  still  more  so  in  alcohol,  condenses  into  a liquid  by  a 
pressure  of  3’ 6 atmospheres  at  45°  Fahrenheit,  as  may  be 
shown  by  heating  with  a lamp  cyanide  of  mercury  in  a bent 
tube,  as  seen  in  Fig.  259  ; the  tube  being  Fig.  259. 
closed  at  both  ends,  liquid  cyanogen  accu- 
mulates at  the  cool  extremity.  Though  a 
compound  body,  it  has  all  the  properties  and 
characters  of  a powerful  electro-negative  ele- 
ment. A farther  description  of  it  and  its 
compounds  will  be  given  under  organic  chemistry. 

BISULPHURET  OF  CARBON,  = 38-28, 
may  be  made  by  passing  the  vapor  of  sulphur  over  char- 
coal ignited  in  a tube,  and  receiving  the  product  in  a cold 
bottle  ; the  apparatus  is  represented  in  Fig.  260.  Into  the 
top  of  a large  iron  bottle,  two  tubes,  h c,  one  straight  and  the 
other  bent,  are  inserted ; the  bottle  having  been  filled  with 
charcoal,  pieces  of  brimstone  are  dropped  in  through  the 
tube  h as  soon  as  the  bottle  is  red  hot.  The  sulphur  and 
carbon  unite.  The  product  passes  along  the  tubes  cf  cooled 

How  is  cyanogen  made  ? How  may  it  be  condensed  into  a liquid  ? How 
is  bisulphuret  of  carbon  formed  ? 


BORON. — -BORACIC  ACID. 


S54 


by  a stream  of  water  from  the  cock,  d,  the  water  being  con- 
ducted by  a string,  h,  into  a basin,  x.  The  vapor  passes 
into  the  bottle,  ?^,  which  is  partially  filled  with  ice,  and  the 
incondensable  gases  pass  out  through  m.  It  is  a transpa- 
rent liquid  of  a very  disagreeable  odor,  has  the  quality  of 
dissolving  sulphur  and  phosphorus,  boils  at  108®  Fahren- 
heit, and  is  therefore  very  volatile. 

BORON,  5 = 10*9, 

was  discovered  by  Davy  as  the  basis  of  boracic  acid,  from 
which  it  may  be  set  free  by  potassium  at  a red  heat.  It 
is  an  olive-colored  solid,  which  burns  when  ignited  in  oxy- 
gen gas  or  atmospheric  air,  and  produces  boracic  acid. 


BORACIC  ACID.  503  = 34*939. 

Boracic  acid  exists  in  the  waters  of  the  volcanic  springs  of 
Tuscany.  It  is  also  brought  from  India  combined  with  soda, 
and  may  be  artificially  procured  by  dissolving  one  part  of  bo- 
rax in  four  of  hot  water,  and  adding  half  apart  of  sulphuric 
acid.  On  cooling,  the  boracic  acid  is  deposited  in  small  crys- 
Fig,  ^61,  talline  scales,  which  may  be  purified 

- by  recrystallization. 

Boracic  acid  melts  at  a red  heat 
_ into  a transparent  glass.  Its  crystals, 

raised  to  212®  Fahrenheit,  lose  half 
, their  water.  It  Volatilizes  readily 

when  boiled  in  water,  is  soluble  in 


::r^)  c 


i rorn  ir,  boron  derived?  How  is  boracio  acid  prepared? 


SILICON.*— SILICIC  ACID. 


5255 


alcohol,  the  solution  burning  with  a green  flame.  The  ex- 
periment may  be  made  in  a glass  instrument  like  Fig.  261, 
a b c.  It  is  a very  feeble  acid,  and  even  turns  yellow  tur- 
meric brown,  like  an  alkali. 

TERFLUORIDE  OF  BORON,  BF^  = 66*94,  i 

is  formed  when  a mixture  of  fluor  spar,  boracic  acid,  and  oil 
of  vitriol  is  heated  in  a flask.  It  is  decomposed  by  water, 
by  which  it  is  rapidly  absorbed.  In  damp  air  it  forms  white 
fumes. 

SILICON.  ,Si==  22-18. 

This  element  may  be  prepared  by  igniting  the  silico-fluo- 
ride  of  potassium  with  potassium,  act-  Fig.  262. 

ing  upon  the  resulting  substance  with 
water,  which  removes  the  fluoride  of 
potassium,  and  leaves  the  silicon  as  a 
nut-brown  powder. 

It  exhibits  two  allotropic  states. 

Prepared  as  first  described,  it  takes 
fire  and  burns  when  heated  in  atmos- 
pheric air ; but  if  previously  ignited  in 
close  vessels,  it  shrinks  in  volume,  and, 
passing  into  its  other  state,  becomes  incombustible  in  ox- 
ygen gas. 

SILICIC  ACID.  ,St03  = 46-219. 

Silicic  acid  is  one  of  the  most  abundant  bodies  in  nature, 
existing  under  the  innumerable  forms  of  the  quartz  miner- 
als, sands,  and  sandstones.  Rock  crystal  and  flint  are  pure 
silicic  acid. 

It  may  be  obtained  in  a more  convenient  form  by  fusing 
white  sand  with  four  parts  of  carbonate  of  potash,  dissolv- 
ing the  resulting  silicate  in  water,  and  decomposing  the  so- 
lution with  hydrochloric  acid.  The  silicic  acid  separates  as 
a gelatinous  hydrate,  slightly  soluble  in  water,  which,  when 
washed  and  dried,  yields  a white  powder  absolutely  insolu- 
ble in  water.  There  is  reason  to  believe  that  the  silicon 
exists  in  its  different  allotropic  states  in  these  two  forms  of 
silicic  acid. 

Silica  is  a gritty  substance,  sufficiently  hard  to  scratch 
glass.  Its  specific  gravity  is  2-66.  It  combines  with  the 

What  is  the  color  it  communicates  to  flame  ? How  may  silicon  be  pre- 
pared ? In  what  respect  does  it  differ  after  ignition  ? What  is  the  constitu- 
tion of  silicic  acid,  and  how  may  it  be  prepared  ? What  are  its  properties  ? 


256 


FL.UORIDE  OF  SILICON. 


alkalies  in  excess  to  form  glass.  It  requires  a higli  temper- 
ature for  fusion.  Hydrofluoric  acid  is  the  only  acid  which 
dissolves  it. 

FLUORIDE  OF  SILICON,  SiFs  = 7S‘22, 
may  he  obtained,  as  just  stated,  by  dissolving  silica  in  hy- 


Fis^.  263. 


drofluoric  acid,  or  by  heating  a 
mixture  of  fluor  spar  and  sa’nd 
with  sulphuric  acid.  It  is  col- 
orless ; fumes  in  the  air ; its  spe- 
cific gravity  is  3*66.  Trans- 
mitted from  the  flask  which 
generates  it,  a,  Figure  263, 
through  water,  it  is  decompos- 
ed, hydrated  silica  being  de- 
j posited.  To  prevent  the  tube 
which  delivers  the  gas  being 
stopped  up  by  the  silica,  some 
quicksilver,  e,  may  be  put  in 
the  vessel,  d,  and  the  tube  dip- 
ped into  it,  so  that  the  bubbles 
of  gas  may  not  come  in  contact 
with  the  water  until  they  have  reached  the  surface  of  the 
metal ; the  sulphuric  acid  may  be  introduced  through  the 
funnel,  L In  the  water,  hydrofluosilicic  acid  forms,  which 
is  sometimes  used  as  a test  for  potash. 

Nitrogen  and  .Hydrogen  yield  three  compounds : 

they  are  designated  respectively  by  the  names 

Amidogen. 

Ammonia. 

Ammonium. 

AMIDOGEN.  iViY2  = 1619. 

Amidogen  is  a hypothetical  compound  radical,  the  exist- 
ence of  which,  in  several  compounds,  is  inferred.  On  heat- 
ing potassium  in  ammoniacal  gas,  one  third  of  the  hydrogen 
is  set  free,  and  an  olive  substance  remains,  the  amidide  of 
potassium.  This,  in  contact  with  water,  yields  potash  and 
ammonia. 

K,  NH^  + HO...  = ...KO  + NH^. 

When,  the  fluoride  of  silicon  is  passed  through  water,  what  are  the  pra- 
ducts?  How  many  compounds  of  nitrogen  and  hydrogen  are  admitted? 
What  is  amidogen  ? 


AMMONIA. 


257 


Amidogen  is  an  electro-negative  compound  radical  like  cy- 
anogen. 


AMMONIA.  iYiJa  = 17-19. 


This  substance,  called  also  'volatile  alkali^  from  its  prop- 
erties, is  an  abundant  product  of  the  putrefaction  of  animal 
matters,  and  may  be  obtained  by  the  destructive  distillation 
of  horn  ; hence  the  term,  spirit  of  hartshorn  : it  also  exists 
in  the  air,  and  is  a common  product  of  many  chemical  re- 
actions. 

It  may  be  obtained  by  heating  in  a flask, 
a,  Fig.  264,  equal  quantities  of  slacked  lime 
and  muriate  of  ammonia,  and,  as  its  specific 
gravity  is  only  0*590,  it  may  be  collected,  as 
in  the  cut,  in  a flask  or  jar,  b,  with  the  mouth 
downward,  by  displacing  the  heavier  air.  The 
action  is 

(NH.  X HCl)  + (CaO,  HO) 

CaCl  + 2HO  + NH^. 


It  is  a transparent  and  colorless  gas,  of  excessive  pun- 
gency, and  having  all  the  qualities  of  a strong  alkali.  It 
turns  turmeric  paper  brown,  is  absorbed  with  wonderful  ra- 
pidity by  water,  which,  at  32°  F.,  takes  up  780  times  its  vol- 
ume of  the  gas,  a result  which  may  be  illustrated  by  invert- 
ing a flask  full  of  it  in  some  cold  water,  when  the  water 
rushes  up  with  sufficient  violence  to  destroy  the  flask  very 
frequently.  Ammonia  neutralizes  the  strongest  acids,  as 
may  be  shown  by  dropping  it  into  litmus  water  which  has 
been  reddened  by  sulphuric  or  nitric  acid. 

It  is  composed  of  three  volumes  of  hydrogen  mg.  265. 
with  one  of  nitrogen,  condensed  into  two  vol- 
umes. It  may  be  recognized  by  its  remarkable 
odor,  and  by  the  formation  of  white  clouds  when 
a rod,  a,  Fig.  265,  dipped  in  muriatic  acid,  is 
approached  to  it.  It  condenses  into  a liquid  at 
60°  under  a pressure  of  6*5  atmospheres. 

Its  solution  in  water,  known  as  aqua  ammoniac,  is  pre- 
pared by  passing  the  gas  evolved  from  slacked  lime  and 
sal  ammoniac  through  Wolfe’s  bottles,  as  is  represented  in 


From  what  substances  may  ammonia  be  procured  ? What  is  the  specific 
gravity  ? .What  class  of  bodies  does  it  closely  resemble  ? How  may  its 
affinity  for  water  be  illustrated  ? How  does  it  act  on  reddened  litmus  water  ? 
What  is  its  constitution  ? How  may  it  be  detected  ? By  what  process  is 
aqua  ammonias  made  ? 


258 


AMMONIUM. 


Fig.  266 ; the  water  will  take  it  up  until  its  specific  gravity 
is  lowered  to  O' 872  ; it  then  contains  32 J per  cent  of  gas. 
This  solution,  somewhat  diluted,  is  much  used  by  chemists 
for  neutralizing  and  precipitating.  It  also  afibrds  the  best 
means  of  obtaining  ammonia,  merely  requiring  to  be  warm- 
ed in  a flask,  when  the  gas  readily  comes  off. 

AMMONIUM,  Am  = iVH4=  18-19, 

is  a hypothetical  body,  and  believed  to  be  of  a metallic  na- 
ture ; its  symbol  is,  therefore.  Am.  It  maybe  combined  with 
mercury  by  decomposing  a solution  of  an  ammoniacal  salt 
by  a Voltaic  current,  the  negative  pole  being  in  contact  with 
a globule  of  that  metal,  or  by  putting  an  amalgam  of  potas- 
sium and  mercury  in  water  of  ammonia.  Under  these  cir- 
cumstances, the  mercury  swells,  and  eventually  becomes  of 
a soft  consistency  like  butter,  preserving  its  metallic  aspect 
completely.  All  attempts  to  separate  the  ammonium  from 
this  amalgam  have  failed.  It  decomposes  into  NH^  and  H, 

It  is  now  generally  agreed  by  chemists  that  ammonium 
is  the  basis  of  the  salts  of  ammonia.  Thus,  sal  ammoniac, 
called  also  the  muriate  of  ammonia,  is  NH^  + HCl;  but 
this  is  evidently  the  same  as  iVAT^  + Cl^  that  is,  the  chlo- 
ride of  ammonium.  In  all  cases  where  ammonia  forms 
neutral  salts  with  the  so-called  oxygen  acids,  it  requires  an 
atom  of  water,  but  this  water  evidently  gives  it  the  con- 
stitution, not  of  iViJg  + HO,  but  NH^  + 'tfi®  water, 

What  is  the  nature  of  ammonium  ? In  what  state  may  it  be  obtained  ? 
How  can  it  be  shown  that  it  is  the  base  of  the  ammonia  salts  ? 


AMMONIUM. 


259 


therefore,  makes  it  oxide  of  ammonium,  which  will  unite 
with  sulphuric,  or  nitric,  or  any  other  acid,  precisely  after 
the  manner  of  any  other  metallic  oxide.  Moreover,  the 
compounds  of  ammonia  with  this  atom  of  water  are  iso- 
morphous  with  the  compounds  of  the  oxide  of  potassium. 
From  these  facts,  therefore,  we  see  that  when  sulphuric 
acid  unites  with  ammonia,  the  atom  of  water  which  the 
acid  contains  gives  to  the  salt  the  constitution 
iVS;,  O + iSOg,  or  NH^  + or  Am  + 
the  latter  formula  being  analogous  to  Am  + Cl,  the  chlo- 
ride of  ammonium  or  sal  ammoniac.  This  view  of  the  na- 
ture of  the  ammonia  compounds  is  known  under  the  name 
of  the  ammonium  theory  of  Berzelius. 

Of  the  compounds  of  ammonium  with  other  bodies,  the 
protosulphuret,  S,  may  be  mentioned  under  the  name 

of  hydrosulphuret  of  ammonia.  It  is  much  used  as  a test. 
There  are  also  other  sulphurets. 


What  is  meant  by  the  ammonium  theory  of  Berzelius  ? 


THE  METALS. 


LECTURE  LVII. 

General  Properties  of  the  Metals. — Definition  of  a 
MetaL — Color,  Specific  Gravity,  Hardness,  Tenacity, 
and  other  Properties. — Relations  to  Heat. — Compounds 
with  other  Bodies. — Division  into  Groups. — The  Ox- 
ides and  their  Reduction. — The  Sulphurets  and  their 
Reduction. 

. Of  the  elementary  bodies,  by  far  the  larger  portion  are 
metallic.  By  a metal  we  mean  a body  which  possesses  that 
peculiar  manner  of  reflecting  light  which  is  known  under 
the  designation  of  metallic  lustre.  It  is  also  a good  con- 
ductor of  electricity  and  heat.  Of  these  there  are  at  least 
forty-two,  and  probably  forty-five,  three  having  been  recent- 
ly discovered. 

Most  of  the  metals  are  of  a white  color,  hut  they  differ 
from  each  other  by  slight  shades,  some  having  a faint  blue 
and  others  a pinkish  tint.  There  are  three  which  are  strik- 
ingly colored : gold,  which  is  yellow,  and  copper  and  tita- 
nium, which  are  red.  In  specific  gravity  they  differ  ex- 
ceedingly ; potassium  is  so  light  as  to  float  upon  water,  and 
iridium  is  twenty-one  times  as  heavy  as  that  liquid. 

Many  of  the  metals  are  malleable,  that  is,  can  be  extend- 
ed into  thin  sheets  under  the  blow  of  a hammer ; others  are 
so  brittle  that  they  may  be  reduced  to  powder  in  a mortar  ; 
some  of  them  are  ductile,  and  may  be  drawn  into  fine  wires, 
the  order  for  malleability  not  being  the  same  as  that  for 
ductility.  Thus,  iron  may  be  drawn  into  fine  wire,  but  can 
not  be  beaten  out  into  such  thin  sheets  as  many  other  met- 
als. Of  all  metals  gold  is  the  most  malleable,  and  platina 
has  been  drawn  into  the  finest  wires. 

In  hardness  the  metals  differ  much.  Potassium  is  so  soft 

What  is  the  definition  of  a metal  ? How  many  metals  are  there  ? What 
is  their  color  commonly?  Which  three  are  the  colored  metals?  Of  the 
metals,  which  is  the  lightest,  the  heaviest,  the  most  malleable,  the  softest, 
the  hardest,  the  most  fusible,  and  the  most  volatile  ? 


PROPERTIES  OF  THE  METALS. 


261 


that  it  may  be  moulded  by  the  fingers,  but  iridium  is  among 
the  hardest  bodies  known.  In  tenacity  or  strength  the  same 
differences  are  seen : of  all  metals  iron  is  the  most  tenacidus. 
The  same  metal  differs  very  much  in  this  respect  at  differ- 
ent temperatures. 

In  their  relations  to  heat,  well-marked  distinctions  also 
may  be  traced.  Mercury  at  all  ordinary  temperatures  is  in 
a melted  condition ; but  platina  can  only  be  fused  before 
the  oxyhydrogen  blow-pipe.  As  respects  volatility,  mercury, 
cadmium,  potassium,  sodium,  zinc,  arsenic,  and  tellurium 
may  be  distilled  or  sublimed  at  a red-heat. 

The  metals  unite  with  electro-negative  bodies  and  with 
each  other.  In  decomposition  by  the  Voltaic  battery,  they 
pass  to  the  negative  pole,  and  are  therefore  described  as 
electro-positive  bodies.  Their  compounds  with  oxygen, 
chlorine,  &c.,  pass  under  the  names  of  oxides,  chlorides, 
&c. ; their  compounds  with  each  other  under  the  name  of 
alloys,  or,  if  mercury  be  present,  of  amalgams.  They  also 
unite  with  sulphur,  phosphorus,  and  carbon. 

Chemical  writers  usually  divide  the  metals  into  groups 
founded  upon  their  relations  with  oxygen  gas.  The  follow- 
ing simple  division  is  the  one  I adopt : 1st.  Metals  which  de- 
compose water  at  common  temperatures ; 2d.  Metals  which 
can  not  decompose  water  at  common  temperatures,  but  do 
it  at  a red  heat ; 3d.  Metals  which  can  not  decompose  water 
at  all. 


1st  Group. 

Cerium. 

Titanium. 

Potassium. 

Manganese. 

Arsenic. 

Sodium. 

Iron. 

Antimony. 

Lithium. 

Nickel. 

Tellurium. 

Barium. 

Cobalt. 

Uranium. 

Strontium. 

Zinc. 

Copper. 

Calcium. 

Cadmium. 

Lead. 

Magnesium. 

Tin. 

Bismuth. 

Silver. 

2d  Group. 

•3d  Group. 

Mercury. 

Aluminum. 

Chromium. 

Gold. 

Glucinum. 

Vanadium. 

Palladium. 

Thorium. 

Tungsten. 

Platinum 

Yttrium. 

Molybdenum. 

Rhodium. 

Zirconium. 

Osmium. 

Iridium. 

Lanthanum. 

Columbium. 

The  older  chemists  divided  the  metals  into  four  classes : 
1st.  Alkaline,  such  as  potassium.  2d.  Earthy,  such  as  mag- 
nesium. 3d.  Imperfect,  as  zinc.  4th.  Noble,  as  gold. 

With  what  other  substances  do  they  unite  ? Into  what  groups  may  they 
be  divided  ? What  is  the  division  formerly  in  use  ? 


262 


METALLIC  OXIDES. 


THE  METALLIC  OXIDES. 

Metallic  substances  unite  with  oxygen  with  different  de- 
grees of  intensity,  and  in  very  different  proportions,  many 
of  them  giving  rise  to  a complete  series  of  oxides,  and  pro- 
ducing, 1st.  Basic  oxides.  2d.  Neutral  or  indifferent  oxides. 
3d.  Metallic  acids. 

1st.  The  basic  oxides  are  commonly  protoxides  or  sesqui- 
oxides,  which  form  neutral  salts  with  hydrogen  acids,  with 
the  production  of  water.  To  form  such  salts,  for  every  atom 
of  oxygen  in  the  base  there  is  required  one  atom  of  acid. 
A basic  protoxide,  therefore,  requires  one  atom  of  acid,  a ses- 
quioxide  three,  and  a deutoxide  two,  to  form  a neutral  salt. 

2d.  The  neutral,  or  indifferent,  oxides  contain  more  oxy- 
gen than  the  base,  and,  when  heated  with  acids,  give  off 
that  oxygen,  a basic  oxide  resulting. 

3d.  The  metallic  acids  always  contain  more  oxygen  ; they 
may  be  sesquioxides,  deutoxides,  teroxides,  or  quadroxides, 
and  are  commonly  formed  by  deflagrating  the  metal  with 
nitrate  of  potash. 


REDUCTION  OF  THE  METALLIC  OXIDES. 

Some  of  the  oxides,  such  as  those  of  mercury,  silver,  and 
gold,  may  be  reduced  by  heat  alone  ; but  the  greater  num- 
ber require  the  conjoint  action  of  carbon,  which,  at  a high 
temperature,  decomposes  them  with  evolution  of  carbonic 
oxide.  Among  powerful  reducing  agents  may  be  mention- 
ed the  formiates  and  the  cyanide  of  potassium,  the  former 
acting  through  the  affinity  of  carbonic  oxide  for  oxygen,  and 
the  latter  through  the  affinity  of  carbon  and  potassium  con- 
jointly. The  deoxydation  of  metals  may  also  be  accom- 
plished by  reducing  agents,  such  as  phosphorous  and  sul- 
phurous acids,  or  by  the  action  of  other  metals;  iron,  for  in- 
stance, will  precipitate  metallic  copper  from  its  solutions. 


Fig.  267. 

^ilT  A lifc 


The  Voltaic  current  affords  a powerful 
means  of  efiecting  the  reduction  of  met- 
als in  philosophical  investigations ; by  its 
aid  the  alkaline  metals  were  originally 
obtained.  The  electrotype,  already  de- 
scribed, is  an  example  of  its  action  ; even 
solutions  of  metallic  salts  are  readily  de- 
composed by  it.  Thus,  if  a glass  jar,  T, 


What  substances  do  metals  yield  with  oxygen  ? How  are  metallic  acids 
commonly  made  ? By  what  processes  may  metallic  oxides  be  reduced  ? 


METALUC  SULPHURETS. 


263 


Fig.  267,  be  divided  into  halves,  and  a paper  diaphragm 
be  introduced  between  them,  the  halves  being  tightly  press- 
ed together  by  the  ring  B B,  if  the  jar  be  filled  with  any 
metallic  solution,  such  as  the  sulphate  of  soda,  and  the  pos- 
itive and  negative  wires  of  the  battery  dipped  in  the  oppo- 
site compartments,  after  a time  the  metallic  oxide  will  be 
found  in  one  of  them  and  the  acid  in  the  other,  a total  de- 
composition having  taken  place. 

THE  METALLIC  SULPHURETS. 

Many  of  these,  such  as  the  sulphurets  of  iron,  lead,  and 
copper,  are  found  abundantly  in  nature  ; or  they  may  be 
made  artificially  by  heating  the  metal  with  sulphur,  or  by 
deoxydizing  metallic  sulphates  by  charcoal  or  hydrogen  gas, 
which  converts  them  into  sulphurets ; or  by  the  action  of 
sulphureted  hydrogen  on  their  oxides,  which  yields  a metal- 
lic sulphuret  and  water.  From  their  solutions  under  these 
circumstances,  iron,  manganese,  zinc,  cobalt,  and  nickel  can 
not  be  precipitated,  though  they  may  by  hydrosulphuret  of 
ammonia. 

The  sulphurets  of  a metal  are  usually  equal  in  number 
and  similar  in  constitution  to  its  oxides ; and  as  oxygen 
compounds  unite  with  each  other  to  produce  oxygen  salts, 
the  sulphurets,  in  like  manner,  also  unite  with  each  other 
to  produce  sulphur  salts. 

REDUCTION  OF  THE  SULPHURETS. 

The  metallic  sulphurets  may  often  be  reduced  by  melt- 
ing them  with  another  metal  having  a more  powerful  affin- 
ity for  sulphur  ; thus,  iron  filings  will  decompose  sulphuret 
of  antimony,  sulphuret  of  iron  forming,  and  antimony  being 
set  free.  On  the  large  scale,  however,  a different  process 
is  resorted  to ; the  sulphuret,  by  roasting,  is  converted  into 
a sulphate,  much  of  the  sulphur  being  expelled  during  the 
process  as  sulphurous  or  sulphuric  acid.  The  resulting  sul- 
phate is  then  acted  upon  by  lime  and  carbon  at  a high  tem- 
perature ; the  lime  decomposes  the  sulphate,  setting  free  the 
metallic  oxide,  which  is  at  once  reduced  by  the  carbon,  the 
sulphate  of  lime  turning  simultaneously  into  the  sulphuret 
of  calcium,  which  floats  on  the  surface  of  the  metal  as  a slag. 

By  what  processes  may  metallic  sulphurets  be  obtained  ? What  metals 
can  not  be  precipitated  by  sulphureted  hydrogen?  What  relation  exists 
between  the  sulphurets  and  oxides?  How  are  the  sulphurets  reduced? 
What  is  the  process  on  a large  scale  ? 


204 


POTASSIUM. 


The  metals  also  unite  with  chlorine,  iodine,  bromine, 
carbon,  phosphorus,  &c.,  and  some  with  hydrogen  and  ni- 
trogen. These  compounds  will  be  described  in  their  proper 
places. 


LECTURE  LVIII. 

Potassium. — Discovery  of,  and  Properties. — Relations  to 
Oxygen  and  Water. — Its  Oxides. — Caustic  Potash. — 
, Tests  for  Potash. — Haloid  Compounds  of  Potassium. 
— Salts  of  the  Protoxide^  the  Carbonate,  Nitrate,  Chlo- 
rate, (^C. 

POTASSIUM.  ic  = 39'15. 

Potassium  was  first  obtained  by  Sir  H.  Davy,  who  de- 
composed its  hydrated  oxide  (potash)  by  a Voltaic  current. 
From  the  positive  pole  oxygen  gas  escaped  in  bubbles,  and 
metallic  potassium  in  globules  appeared  at  the  negative. 

It  was  subsequently  discovered  that  the  same  substance 
could  be  decomposed  by  iron,  and  also  by  carbon  at  a high 
temperature  ; and  the  latter  of  these  substances  is  now  ex- 
clusively resorted  to  for  the  preparation  of  potassium.  The 
carbonate  of  potash  is  ignited  with  charcoal  in  an  iron  bot- 
tle, and  the  potassium  received  into  a vessel  containing 
naphtha.  The  productiveness  of  the  operation  is  greatly 
interfered  with  by  the  circumstance  that  the  carbonic  oxide 
which  is  evolved,  as  it  cools  below  a red  heat,  unites  with 
much  of  the  potassium,  producing  a gray  substance,  which 
chokes  the  tubes  and  diminishes  the  yield  of  the  metal. 

Potassium  is  a bluish  white  metal,  which,  at  32°  F.,  is 
brittle,  melts  at  150°  F.,  and  boils  at  a red  heat,  yielding 
a green  vapor.  Its  specific  gravity  is  *865  ; it  is,  there- 
Fi^.  268.  fore,  much  lighter  than  water,  on  the  surface 
of  which  it  floats.  At  70°  F.  it  may  be  mould- 
ed by  the  fingers,  being  soft  and  pasty. 

It  possesses  an  intense  affinity  for  oxygen, 
and  hence  requires  to  be  preserved  in  bottles 
containing  naphtha.  A piece  of  it  thrown 

From  what  was  potassium  first  obtained?  What  process  is  now  in  use 
for  its  preparation  ? What  circumstance  interferes  with  the  productiveness 
ofthis  process  ? What  are  the  properties  of  potassium  ? 


OXIDES  OF  POTASSIUM. 


265 


upon  water  takes  fire,  and  burns  with  a beautiful  pink  flame. 
In  the  air  it  speedily  tarnishes,  and,  oven  when  brought  in 
contact  with  ice,  it  decomposes  it  with  the  evolution  of 
flame.  In  these  cases  the  combustion  arises  from  the  hy- 
drogen uniting  with  the  oxygen  of  the  air  and  reproducing 
water ; the  potassium  simultaneously  burns. 

POTASSIUM  AND  OXYGEN. 

There  are  two  oxides  of  potassium,  a protoxide  and  a per- 
oxide, 

KO.,.  KO^. 

The  affinity  of  potassium  for  oxygen  is  so  great  that  it  takes 
that  substance  from  almost  all  other  bodies,  and  hence  is 
used  as  a powerful  deoxydizing  agent. 

Protoxide  of  Potassium.  KO  = 47  T 6 3 . 

This  substance  can  only  be  formed  by  the  action  of  po- 
tassium on  dry  air  or  oxygen.  It  possesses  a great  affinity 
for  water,  and  is  converted  by  it  into  the  hydrated  oxide  of 
potassium,  commonly  called  caustic  potash. 

Hydrated  Oxide  of  Potassium.  KO,  HO  = 56*176. 

This  substance  is  best  procured  by  boiling  two  parts  of 
pure  carbonate  of  potash  with  twenty  of  water,  and  having 
previously  slacked  one  part  of  quicklime  with  hot  water, 
the  cream  which  it  forms  is  to  be  added  by  degrees,  and  the 
whole  boiled.  The  process  should  be  conducted  in  an  iron 
vessel  to  which  a lid  can  be  adapted,  so  as  to  exclude  the 
air  during  cooling ; the  resulting  carbonate  of  lime  settles 
perfectly,  and  the  hydrate  may  be  obtained  by  evaporating 
the  solution  rapidly  in  a silver  vessel,  pouring  out  the  melt- 
ed residue  on  a silver  plate,  or  casting  it  into  the  form  of 
small  cylinders. 

The  decomposition  which  takes  place  in  the  foregoing 
process  is  simple, 

KO,  CO.,,  + CaO,  HO...=  ...  CaO,  CO,  + KO,  HO; 
that  is,  the  lime  takes  carbonic  acid  from  the  carbonate  of 
potash,  and  the  oxide  of  potassium  unites  with  water.  The 
solution  may  be  known  to  be  free  from  carbonic  acid  by  not 
effervescing  when  mixed  with  stronger  acids. 

The  hydrate  of  potash  is  a white  solid,  having  a power- 

How  many  oxides  does  it  form?  How  is  the  hydrated  oxide,  or  caustic 
potash,  obtained  ? What  is  the  nature  of  the  decomposition  ? Of  what  prop- 
erties is  the  hydrate  of  potash  possessed,  and  what  are  its  uses  ? 

M 


266 


OXIDES  OF  POTASSIUM. 


ful  affinity  for  water,  and  abstracting  it  rapidly  from  the 
air.  Taken  between  the  fingers,  it  commnnieates  to  the 
skin  a soft  feel,  and,  if  a concentrated  solntion  be  used,  soon 
effects  a disorganization ; hence  it  is  used  by  surgeons  in 
the  form  of  small  sticks  as  an  escharotie.  It  possesses  pre- 
eminently the  alkaline  qualities,  and,  indeed,  may  be  takeni 
as  the  type  of  that  class  of  bodies,  neutralizes  the  most  pow- 
erful acids  perfectly,  and  communicates  to  turmeric  paper, 
or  turmeric  solution,  a brown  tint.  It  turns  the  infusion  of 
red  cabbage  green,  and,  possessing  an  intense  affinity  for  car- 
bonic acid,  is  used  in  organic  analysis  to  absorb  that  gas. 

Potash  in  combination  occurs  in  all  fertile  soils,  and  is 
essential  to  the  growth  of  land  plants,  from  the  ashes  of 
which  its  carbonate  is  abundantly  procured.  This  may  be 
shown  by  filtering  water  through  the  ashes  of  wood,  when 
the  clear  liquid  will  be  found  to  answer  to  all  the  tests  in- 
dicating the  presence  of  potash.  It  occurs  also  abundantly 
in  feldspar,  and  hence  is  found  in  clays.  The  want  of  fer- 
tility in  soils  appears  occasionally  to  be  due  to  the  absence 
of  this  body. 

The  bichloride  of  platinum  gives,  with  a solution  of  pot- 
ash, a yellow  precipitate  of  the  chloride  of  platinum  dnd 
potassium.  When  the  amount  of  potash  is  small,  it  is  well 
to  add  alcohol  at  first,  in  v/hich  the  double  chloride  is  in- 
soluble. Ammonia  yields  a similar  precipitate;  but  this 
may  be  avoided  by  exposing  the  substance,  in  the  first  in- 
stance, to  a red  heat  before  testing.  Perchloric  acid,  with 
alcohol,  yields  a white  precipitate.  Tartaric  acid,  if  added 
in  excess,  and  the  mixture  stirred  with  a glass  rod,  bearing 
gently  on  the  sides  of  the  vessel,  gives  white  streaks  of  the 
bitartrate  of  potash  'wherever  the  rod  has  passed  over  the 
glass. 

Of  other  compounds  of  potassium,  the  following  may  be 
mentioned  : 


Peroxide  of  potassium,  KO^. 
Chloride  of  potassium,  KCl. 
Iodide  of  potassium,  KI. 


Bromide  of  potassium,  KBr. 
Protosulphuret  af  potassium,  KS. 
PcBtasulphuret  of  potassium,  KS^ 


It  also  combines  with  hydrogen  in  two  proportions,  pro- 
ducing a solid  and  a gas,  the  latter  of  which  takes  fire 
spontaneously  in  the  air. 


How  may  the  existence  of  potash  in  the  ashes  of  plants  be  proved** 
What  are  the  tests  for  the  presenee  of  the  substance?  Name  some  of  its 
other  compounds. 


SALTS  OF  POTASH. 


267 


Of  these  compounds,  the  most  important  are  the  peroxide 
of  potassium,  which  is  formed  by  passing  oxygen  over  red- 
hot  potash ; it  is  decomposed  by  water,  evolving  oxygen 
and  producing  potash  ; the  chloride  of  potassium,  which  is 
analogous  to  common  salt ; the  iodide,  much  of  which  is 
consumed  in  medicine,  under  the  name  of  hydriodate  of 
potash.  It  may  be  prepared  by  dissolving  iodine  in  a so- 
lution of  potash  till  the  liquid  begins  to  appear  brown,  then 
evaporating  to  dryness,  and  igniting  the  residue  : oxygen  is 
evolved,  and  iodide  of  potassium  remains  ; it  may  be  then 
dissolved  in  water,  and  crystallized.  It  is  white,  crystal- 
lizes in  cubes,  and  is  very  soluble  in  water  and  hot  alcohol. 
Its  solution  will  dissolve  large  quantities  of  iodine.  The 
pentasulphuret  is  the  chief  ingredient  of  liver  of  sulphur, 
which  is  formed  by  fusing  sulphur  with  carbonate  of  potash 
at  a low  temperature. 

SALTS  OF  THE  PROTOXIDE  OF  POTASSIUM. 

Carbonate  of  Potash  is  obtained  by  lixiviating  the  ashes 
of  plants.  In  an  impure  state  it  forms  the  potashes  and 
pearlashes  of  commerce.  It  may  be  obtained  pure  by  ig- 
niting the  bitartrate  with  half  its  weight  of  the  nitrate  of 
potash.  It  has  an  alkaline  taste,  its  solution  feels  greasy 
to  the  fingers,  it  is  very  soluble  in  water,  and  deliquescent. 

Bicarbonate  of  Potash ^ formed  by  transmitting  a stream 
of  carbonic  acid  through  a solution  of  the  former  salt.  It 
crystallizes  in  eight-sided  prisms  with  dihedral  summits. 

Sulphate  of  Potash,  formed  by  neutralizing  the  follow- 
ing salt.  Crystallizes  in  anhydrous,  oblique,  four-sided 
prisms,  soluble  in  about  ten  times  its  weight  of  water. 

Sulphate  of  Potash  and  Water,  sometimes  designated 
as  the  bisulphate  of  potash  ; it  is  the  residue  of  the  produc- 
tion of  nitric  acid.  It  is  soluble  in  water,  and  has  an  acid 
reaction.  It  crystallizes  in  rhombohedrons. 

Nitrate  of  Potash  is  extracted  on  the  large  scale  from 
certain  soils  in  which  organic  matter  is  decaying  in  contact 
with  potash.  It  crystallizes  in  six-sided  prisms,  fuses  at  a 
heat  beneath  redness,  with  evolution  of  oxygen  gas.  It  is 
soluble  in  about  three  times  its  weight  of  water,  at  common 
temperatures.  This  salt  enters  as  an  essential  ingredient  in 
gunpowder,  which  is  composed  of  about  one  atom  of  nitrate 


What  are  the  properties  of  the  iodide  ? From  what  is  the  carbonate  ob- 
tained ? What  is  the  origin  and  use  of  the  nitrate  ? 


268 


SALTS  OF  POTASH. SODIUM. 


of  potash,  one  of  sulphur,  and  three  of  carbon.  The  sulphur 
of  this  mixture  accelerates  the  combustion,  while  the  oxy- 
gen of  the  nitre  forms  carbonic  acid  with  the  charcoal.  The 
products,  therefore,  of  the  perfect  combustion  of  gunpowder 
are  carbonic  acid,  nitrogen,  and  the  sulphuret  of  potassium. 
It  commonly  happens,  however,  that  sulphate  of  potash  is 
formed.  The  proportions  of  the  ingredients  of  gunpowder 
are  varied  for  different  uses.  The  powder  used  for  mining, 
for  example,  contains  more  sulphur  than  that  used  for  fire- 
arms. 

Chlorate  of  Potash. — When  a stream  of  chlorine  is  pass- 
ed into  a solution  of  potash,  the  chloride  of  potassium  and 
the  chlorate  of  potash  result ; the  latter  is  deposited  in  flat, 
scaly  crystals. 

The  chlorate  of  potash  contains  no  water  ; it  dissolves  in 
about  fifteen  times  its  weight  of  that  fluid  ; melts  at  a red 
heat,  with  evolution  of  pure  oxygen  ; deflagrates  with  com- 
bustible bodies,  sometimes  with  much  violence. 


LECTUHE  LIX. 

Sodium. — Preparation  of. — Relation  to  Oxygen  and  Wa- 
ter.— Color  communicated  to  Flame. — Its  Oxides. — 
The  Hydrated  Oxide.  — Tests  for  Sodium. — Haloid 
Compounds. — Common  Salt. — Salts  of  the  Protoxides ^ 
Carbonates^  Sulphates,  Nitrates,  Sfc. — Lithium. — Ba- 
rium.— Its  Oxides. — Haloid  Compounds. — Salts  of  the 
Protoxide. 

SODIUM.  Na  = 23'3. 

Sodium  may  be  obtained  by  the  same  process  as  potas- 
sium, but  is  best  procured  by  igniting  the  calcined  acetate 
of  soda  with  powdered  charcoal  in  an  iron  bottle ; and,  as 
the  sodium  does  not  act  upon  carbonic  oxide,  the  operation 
is  much  more  productive  than  in  the  case  of  the  other  met- 
al. Like  potassium,  it  is  to  be  kept  in  bottles  under  the 
surface  of  naphtha. 

In  color,  sodium  resembles  silver ; its  spe.cifie  gravity  is 
0*9348;  it  therefore  floats  upon  water.  It  melts  at  194° 

How  is  the  chlorate  of  potash  made  ? How  is  sodium  obtained,  and 
what  are  its  uses  ? What  are  its  properties  compared  with  potassium  ? 


OXIDES  OF  SODIUM. 


2H9 


F.,  and  is  more  volatile  than  potassium.  Thrown  upon 
water,  it  decomposes  it  with  a hissing  sound,  and  with  the 
evolution  of  hydrogen,  but  no  flame  appears.  If,  however, 
the  water  is  hot,  then  a beautiful  yellow  flame,  character- 
istic of  sodium  and  its  compounds,  is  the  result. 

SODIUM  AND  OXYGEN. 

With  oxygen  sodium  forms  three  compounds  : the  suhox- 
ide,  protoxide,  and  peroxide. 

Trotoxide  of  Sodium.  iVhO  = 31-313. 

This,  like  the  corresponding  potassium  compound,  is  pro- 
duced by  oxydizing  sodium  in  dry  air.  It  is  a white  pow- 
der, which  attracts  moisture  from  the  air  and  forms  the  hy- 
drated oxide  of  sodium,  commonly  called  caustic  soda. 

Hydrated  Oxide  of  Sodium ^ NaO  + HO  = 40-323, 
or  caustic  soda,  may  he  made  by  the  same  process  as  that 
given  for  caustic  potash,  by  using  carbonate  of  soda,  and, 
when  the  resulting  carbonate  of  lime  has  settled,  evaporat- 
ing the  liquid.  The  best  proportions  are  one  part  of  quick- 
lime to  five  of  carbonate  of  soda  in  crystals. 

Caustic  soda  resembles  caustic  potash  in  most  of  its  prop- 
erties. It  is  deliquescent,  has  a strong  affinity  for  carbonic 
acid,  and  acts  upon  animal  tissues  as  an  escharotic.  Its 
salts  are  generally  more  soluble  than  the  potash  salts,  and 
on  this  are  founded  the  methods  recommended  for  distin- 
guishing the  latter  compounds  from  it.  Moreover,  the  soda 
compounds  communicate  to  the  flame  of  alcohol,  or  to  the 
blow-pipe,  a yellow  color : the  same  tint  which  is  charac- 
teristically seen  when  sodium  is  placed  in  hot  water. 

Chloride  of  Sodium.  NaCl  — 58-77, 

The  chloride  of  sodium,  common  salt,  is  obtained  abund- 
antly from  the  waters  of  the  sea,  to  which  it  gives  their  sa- 
linity. It  is  also  found  as  rock  salt,  deposited  extensively 
in  certain  geological  formations. 

Common  salt  is  the  general  type  of  that  extensive  class 
of  compounds  which  have  derived  the  name  of  salt  bodies 
from  it.  It  crystallizes  in  cubes,  and,  when  in  mass,  is  often 
perfectly  transparent,  and  permits  the  passage  of  heat  of 

What  compounds  with  oxygen  does  it  give  ? How  is  caustic  soda  ob- 
tained ? What  are  its  properties  and  uses  ? What  color  do  the  sodium 
compounds  give  to  flarpe  ? What  is  the  constitution  of  common  salt  ? From 
what  sources  is  it  derived  ? What  are  its  properties  ? 


270 


SALTS  OP  SODA. 


every  temperature  through  it  freely.  It  melts  into  a liquid 
at  a red  heat,  crystallizes  in  cubes,  and  is  not  more  soluble 
in  hot  than  cold  water.  It  is  extensively  used  in  the  prep- 
aration of  hydrochloric  acid  and  chlorine ; immense  quan- 
tities, also,  are  annually  consumed  in  the  preparation  of  car- 
bonate of  soda,  which  is  made  by  first  acting  on  the  com- 
mon salt  with  oil  of  vitriol,  so  as  to  turn  it  into  sulphate  of 
soda,  and  igniting  this  with  charcoal  and  carbonate  of  lime: 
an  impure  carbonate  of  soda  is  the  result,  known  under  the 
name  of  black  ash,  or  British  barilla.  Common  salt  is  extens- 
ively used  for  the  curing  of  meat.  It  is  also  an  essential  article 
of  food,  being  decomposed  in  the  animal  system,  and  furnish- 
ing hydrochloric  acid  to  the  gastric  juice  and  soda  to  the  bile. 

The  compounds  of  sodium  with  bromine,  iodine,  sulphur, 
&c.,  are  not  of  interest. 

SALTS  OF  THE  PROTOXIDE  OF  SODIUM. 

Carbonate  of  Soda  is  sometimes  obtained  by  lixiviating 
the  ashes  of  sea- weeds.  Large  quantities  are  also  procured 
from  the  decomposition  of  sulphate  of  soda  by  saw-dust  and 
lime  at  a high  temperature,  the  carbonaceous  matter  de- 
composing the  sulphuric  acid  and  generating  carbonic  acid, 
which  unites  with  the  soda,  while  the  liberated  sulphur  is 
partly  dissipated  and  partly  unites  with  the  calcium.  From 
the  resulting  mass  carbonate  of  soda  is  obtained  by  lixivia- 
tion.  The  crystals,  as  found  in  commerce,  contain  general- 
ly ten  ounces  of  water ; there  are  two  other  varieties,  the 
one  containing  eight  atoms,  and  the  other  one  atom  of  water. 
Large  quantities  of  the  carbonate  of  soda  are  also  sold  in  an 
uncrystallized  state,  under  the  name  of  salts  of  soda.  The 
figure  of  the  crystals  of  this  salt  is  a rhombic  octahedron. 
They  effloresce  on  exposure  to  the  air.  They  are  soluble 
in  five  times  their  weight  of  cold  and  in  less  than  their  own 
weight  of  boiling  water. 

Bicarbonate  of  Soda,  or  the  double  carbonate  of  soda 
and  water,  is  formed  by  transmitting  a stream  of  carbonic 
acid  through  a solution  of  the  carbonate,  and  is  in  the  form 
of  a white  powder.  It  is  less  soluble  in  water  than  the 
former.  There  is  a sesquicarbonate,  which  passes  in  Com- 
merce under  the  name  of  trona. 


How  is  barilla  obtained  from  common  salt  ? Why  is  it  essential  as  an 
article  of  food  ? From  what  source  is  the  carbonate  of  soda  obtained  ? l3e- 
gcribe  the  preparation  of  it  from  the  sulphate. 


SALTS  OF  SODA. 


271 


Sulphate  of  Soda  is  the  Glauber’s  salt  of  the  shops  ; oc- 
curs as  a natural  product,  and  also  as  the  result  of  the  prep- 
aration of  hydrochloric  acid.  It  is  in  prismatic  crystals  of 
a bitter  taste,  efflorescing  in  the  air,  and  becoming  anhy- 
drous. Water  dissolves  more  than  half  its  weight  of  this 
salt  at  91^°  F.,  but  above  that  degree  it  is  less  soluble* 
When  a solution  of  three  parts  of  this  salt  in  two  parts  of 
water  is  corked  up  in  a flask  while  boiling,  it  may  be  cooled 
without  crystallization  taking  place  ; but  if  the  cork  is  with- 
drawn, crystallization  commences  at  once,  or  if  it  does  not, 
the  introduction  of  any  solid  matter  produces  it,  and  the 
temperature  of  the  solution  at  once  rises. 

Nitrate  of  Soda  is  found  abundantly  in  different  parts 
of  America  in  the  soil ; it  crystallizes  in  rhomboids,  dissolves 
in  twice  its  weight  of  cold  water,  and,  from  its  deliques- 
cence, can  not  be  used  in  the  manufacture  of  gunpowder. 

Phosphate  of  Soda  {tribasic)  is  formed  by  neutralizing 
phosphoric  acid  with  carbonate  of  soda  ; two  of  the  hydro- 
gen atoms  are  replaced ; it  crystallizes  in  oblique  rhombic 
prisms,  dissolves  in  three  times  its  weight  of  cold  water,  is 
of  an  alkaline  taste,  and  gives  a lemon-yellow  precipitate 
with  nitrate  of  silver.  By  the  addition  of  soda  to  it  a sub- 
phosphate is  formed,  in  which  all  three  of  the  hydrogen 
atoms  of  the  acid  are  replaced  ; but  by  the  addition  of  phos- 
phoric acid  to  the  ordinary  phosphate,  till  it  ceases  to  give 
any  precipitate  with  chloride  of  barium,  the  biphosphate  of 
soda  results,  a salt  very  soluble  in  water.  Its  crystals  are 
rhombic  prisms.  In  it  only  one  of  the  hydrogen  atoms  is 
replaced. 

Microcosmic  Salt,  or  the  phosphate  of  soda,  ammonia, 
and  water,  is  made  by  dissolving  seven  parts  of  phosphate 
of  soda  in  two  parts  of  water,  and  adding  one  part  of  sal 
ammoniac.  At  a low  heat  it  parts  with  its  water  of  crys- 
tallization, and  the  temperature  rising,  it  loses  its  ammonia 
and  saline  water,  becoming  monobasic  phosphate  of  soda. 
It  is  nauch  used  in  blow-pipe  experiments. 

Pyrophosphate  of  Soda  (bibasic)  is  procured  by  heating 
the  phosphate.  It  gives  a white  precipitate  with  nitrate 
of  silver. 

What  ig  the  cemmefcial  name  ef  the  sulphate  of  soda  ? Wliat  pecu- 
liarity is  there  in  the  crystallization  of  its  solution  ? Why  can  not  the 
nitrate  be  used  for  gunpowder?  What  is  the  difference  between  the  phos- 
phate, the  pyrophosphate,  and  the  metaphosphate  of  soda  ? What  is  micro  • 
cosmic  salt  ? 


272 


LITHIUM. BARIUM. 


Metaphosjphate  of  Soda  (monobasic)  is  formed  by  heat- 
ing microcosmic  salt  to  redness.  It  is  soluble  in  water, 
melts  at  a red  heat,  and  gives,  with  dilute  solutions  of  the 
earthy  and  metallic  salts,  viscid  precipitates,  t 

Biborate  of  Soda,  the  borax  of  the  shops.  It  is  import- 
ed in  a crude  state  from  the  East  Indies,  and  manufactured 
from  the  natural  boracic  acid  of  Italy  by  the  addition  of 
carbonate  of  soda.  It  crystallizes  in  octahedrons,  or  in  ob- 
lique prisms,  the  former  containing  five,  the  latter  ten  atoms 
of  water,  all  of  which  is  lost  by  exposure  to  a red  heat,  the 
salt  then  fusing  into  a glass.  It  is  of  great  use  in  blow- 
pipe experiments. 

LITHIUM.  i = 6-42. 

This  rare  metal  occurs  in  certain  minerals,  such  as  spodu- 
mene,  lepidolite,  &c.  It  is  a white  metal,  communicating 
to  flame  a red  color.  It  yields  a protoxide,  the  carbonate 
of  which  is  of  sparing  solubility  in  water,  thus  forming  the 
link  of  connection  between  the  potash  and  soda  carbonates, 
which  are  very  soluble,  and  the  carbonates  of  the  alkaline 
earths,  as  baryta  and  strontia,  which  are  insoluble. 

This  brings  us  to  the  metals  of  the  alkaline  earths,  which 
form  a division  of  our  first  group  ; Ihe  first  of  these  is 

BARIUM.  Ra  = 68*7. 

The  existence  of  barium  was  first  proved  by  Davy,  who 
isolated  it  by  electrifying  mercury  in  contact  with  the  hy 
drate  of  baryta ; an  amalgam  formed,  from  which  the  mer 
cury  was  subsequently  distilled,  leaving  the  barium  as  a 
metal  of  a gray  color  like  cast  iron,  heavier  than  sulphuric 
acid,  in  which  it  sinks,  obtaining  oxygen  rapidly  from  the 
air,  and  giving  rise  to  the  production  of  the  protoxide  of 
barium,  baryta. 

Protoxide  of  Barium,  Ba  O = 7 6 • 7 1 3 , 
may  be  obtained  by  igniting  the  nitrate  of  baryta,  the  de- 
composition being 

BaO,  .,.Ba0  + N0^+0; 

that  is,  one  atom  of  nitrate  of  barytes  yields  one  of  protox- 

From  what  source  is  borax  derived,  and  what  are  its  uses  ? In  what 
minerals  does  lithium  occur  ? What  is  the  relation  of  its  carbonate  to  those 
of  the  preceding  and  subsequent  metals  ? How  was  barium  first  obtained  f 
What  is  the  process  for  obtaining  the  protoxide,  and  also  its  hydrate  ? 


OXIDES  OF  BARIUM.  273 

ide  of  barium,  and  one  of  nitrous  acid  and  one  of  oxygen  gas 
are  expelled. 

This  protoxide  is  a white  colored  body,  possessing  a strong 
affinity  for  water,  with  which  it  exhibits  the  phenomenon 
of  slacking,  as  is  the  case  to  a less  extent  with  lime,  heat 
being  evolved.  It  has  an  acid  taste,  is  soluble  in  water, 
and  absorbs  carbonic  acid  from  the  air.  Its  specific  gravity 
is  about  4-000.  Its  soluble  salts  are  poisonous. 

Hydrate  of  Baryta,  BaO,  HO  = 85*726, 
is  formed  by  slacking  the  protoxide,  and  is  a wffiite  powder, 
very  soluble  in  hot,  but  less  so  in  cold  water,  yielding,  there- 
fore, crystals  when  a hot  solution  cools : these  contain  nine 
atoms  of  water  of  crystallization.  The  cold  solution  is  used 
as  a test  for  carbonic  and  sulphuric  acids,  with  which  it 
forms  insoluble  white  precipitates. 

This  solution  is  most  easily  obtained  by  calcining  the  na- 
tive sulphate  with  pulverized  charcoal,  which  converts  it 
into  the  sulphuret  of  barium.  To  a boiling  solution  of  this 
body  oxide  of  copper  is  added  till  the  liquid  ceases  to  black- 
en a solution  of  acetate  of  lead.  On  being  filtered,  the  so- 
lution of  hydrate  of  barytes  is  obtained. 

Peroxide  of  Barium,  BaO^  = 84-7, 

IS  made  by  igniting  chlorate  of  potash  with  barytes,  or  by 
passing  oxygen  over  barytes  in  a red-hot  tube.  It  is  used 
in  the  preparation  of  peroxide  of  hydrogen. 

Of  the  other  compounds  of  barium,  the  chloride  is  much 
used  as  a test  for  sulphuric  acid  ; it  may  be  made  by  de- 
composing carbonate  of  baryta  by  hydrochloric  acid.  The 
sulphuret  of  barium  is  made  by  igniting  the  sulphate  of 
baryta,  heavy  spar,  with  charcoal,  which  deoxydizes  both 
the  sulphuric  acid  and  the  baryta.  It  dissolves  in  hot  wa- 
ter, and  from  this  solution  a solution  of  caustic  baryta  may 
be  obtained  by  boiling  with  the  oxides  of  lead  or  copper,  and 
separating  the  sulphurets  of  those  metals  by  filtration.  By 
acting  upon  it  with  hydrochloric  or  nitric  acid,  the  chloride 
or  nitrate  of  baryta  may  be  prepared. 

SALTS  OF  THE  PROTOXIDE  OF  BARIUM. 

Carbonate  of  Baryta  is  found  native,  as  the  mineral 

What  acids  is  a solution  of  baryta  used  to  detect  ? How  is  the  perox- 
ide made  ? What  is  its  use  ? For  what  purpose  is  the  chloride  of  barium 
employed  ? 

M2 


274 


STRONTIUM. 


Witherite,  and  may  be  prepared  by  precipitating  a soluble 
salt  of  baryta  with  an  alkaline  carbonate.  It  is  soluble  in 
4300  times  its  weight  of  cold  water,  and  2300  of  boiling 
water. 

Sulphate  of  Baryta,  found  native  abundantly  as  heavy 
spar,  and  from  it  most  of  the  compounds  of  barium  are 
prepared.  It  is  called  heavy  spar,  its  density  being  4*47. 
It  crystallizes  generally  in  tabular  plates,  and  is  wholly  in- 
soluble in  water. 


LECTURE  LX. 

Strontium. — Uses  in  Pyrotechny . — Salts  of  Protoxide. — 
Calcium. — Protoxide  of — Sources  in  Nature. — Tests 
for. — Haloid  Ccnnpounds,  Chloride,  Fluoride,  Sulphur- 
ets,  SfC. — Salts  of  the  Protoxide,  Carbonate,  Sidphate, 
Phosphate,  CMoride.  — Magnesium.  — Protoxide.  — 
Salts  of  Protoxide,  Carbonate,  Sulphate,  Double  Phos- 
phate. — Aluminum.  — Sesquioxide.  — Uses  in  the  Arts. 
— Tests. — Salts  of  the  Sesquioxide,  Double  Sulphate, 
Alum. — Manufacture  of  Porcelain  and  Glass. — Other 
Metals. 

STRONTIUM.  Sr  = 43*8.  ^ 

This  metal  may  be  obtained  by  the  same  processes  which 
have  been  used  for  obtaining  barium,  with  which  it  has  a 
considerable  analogy.  Its  natural  compounds  are  the  sul- 
phate and  carbonate,  from  which  its  other  preparations  may 
be  obtained. 

Strontium  yields  a protoxide,  which  is  the  basis  of  a se- 
ries of  salts,  differing  from  baryta  salts  in  not  being  poison- 
ous. The  chloride  and  nitrate  are  used  in  pyrotechny  for 
the  purpose  of  communicating  to  flame  a brilliant  crimson 
color.  The  red  fire  of  theatres  contains  the  latter  salt,  and 
the  former,  if  dissolved  in  alcohol,  communicates  to  its  flame 
the  characteristic  test  of  the  strontium  compounds. 

How  may  the  sulphate  of  barytes  be  converted  into  the  sulphuret  of 
barium?  What  are  the  properties  of  the  carbonate  and  sulphate  of  baryta? 
In  what  respect  does  strontium  differ  from  barium  ? What  is  the  color  it 
communicates  to  flame  ? 


CALCIUM. 


275 


SALTS  OF  THE  PROTOXIDE  OF  STRONTIUM. 

Carbonate  of  Stroniia  is  the  strontianite  of  mineralo- 
gists. 

Sulphate  of  Strontia  is  the  celestine  of  mineralogists. 
It  is  not  so  heavy  as  sulphate  of  baryta,  and  is  said  to  be 
soluble  in  about  4000  times  its  weight  of  boiling  water. 

Nitrate  of  Strontia  forms  an  ingredient  of  the  red  fire 
used  in  theatres  ; it  crystallizes  in  octahedrons,  and  is  solu- 
ble in  five  times  its  weight  of  cold  water,  and  half  its  weight 
of  boiling  water. 

CALCIUM.  Ca  = 20*5. 

Calcium  has  never  been  obtained  in  quantities  sufficient 
to  permit  a full  examination  of  its  properties.  It  oxydizes 
with  rapidity,  yielding  a protoxide,  known  also  as  quicklime 
or  lime. 

Lime  occurs  as  a carbonate  in  the  various  limestones, 
marbles,  chalks,  &c.,  which  form  in  many  countries  exten- 
sive mountain  ranges.  Its  other  salts  are  very  abundant. 

From  the  carbonate,  pure  or  quicklime  may  be  obtained 
by  exposure  to  a bright  red  heat.  If  the  limestone  contains 
silica,  it  may,  however,  be  overburnt,  a silicate  of  lime 
forming,  which  prevents  the  product  from  slacking.  It 
possesses  a strong  affinity  for  water,  and  unites  therewith 
with  a great  elevation  of  temperature,  as  exhibited  in  the 
process  of  slacking.  Exposed  to  a high  temperature,  it 
phosphoresces  splendidly.  The  hydrate  which  forms  when 
lime  is  slacked  is  white ; it  is  soluble  to  a small  extent  in 
water  ; and  it  is  remarkable  that  cold  water  dissolves 
much  more  than  hot.  Lime-water  is  colorless,  of  a partial- 
ly caustic  taste,  neutralizes  acids  perfectly,  restoring  to  red- 
dened litmus  its  blue  color.  It  is  used  as  a test  for  carbon- 
ic acid,  with  which  it  gives  the  white  carbonate  of  lime. 
Milk  of  lime  is  nothing  but  lime-water  in  which  hydrate 
of  lime  is  mechanically  suspended.  The  hardening  of  lime 
mortars  depends  chiefly  on  the  absorption  of  carbonic  acid. 
Hydraulic  lime  possesses  the  quality  of  setting  under  water. 
It  contains  oxide  of  iron,  alumina,  and  silica. 

Lime  is  best  detected  by  oxalate  of  ammonia,  with  which 

What  are  the  mineralogical  names  of  the  carbonate  and  sulphate  of  stron 
tia?  What  is  lime  ? Under  what  forms  does  it  occur  in  nature  ? From 
the  carbonate,  how  may  lime  be  produced  ? What,  is  the  action  of  water 
»n  it  ? What  are  the  properties  of  lime-w'ater?  What  is  milk  of  lime  t 


276 


COMPOUNDS  OF  CALCIUM. 


it  gives  a white  precipitate  of  oxalate  of  lime,  provided  the 
solution  be  not  acid. 

Among  other  compounds  of  calcium  may  be  mentioned 

Chloride  of  Calcium,  CaCl  = 55*97, 
foi*med  by  dissolving  carbonate  of  lime  in  hydrochloric  acid, 
evaporating  the  solution  to  a sirup,  and,  on  cooling,  the 
chloride  crystallizes.  It  is  exceedingly  deliquescent.  Chlo- 
ride of  calcium,  dried  without  crystallizatign,  is  used  in  or- 
ganic analysis  for  collecting  water,  and,  generally,  in  other 
chemical  operations  for  drying  gases. 

Fluoride  of  Calcium,  CaF  = 39*24, 
called,  also,  fluor  spar,  and  frequently  found  as  a mineral 
associated  with  lead.  Crystallizes  in  cubes,  octahedrons, 
&c.,  of  various  colors.  It  is  found  in  fossil,  and,  to  a small- 
er extent,  in  recent  bones.  It  is  used  for  various  ornament- 
al purposes,  and  is  the  source  from  which  the  compounds 
of  fluorine  are  derived. 

Sulphur et  of  Calcium,  CaS  = 36*62, 
obtained  by  igniting  the  sulphate  of  lime  with  charcoal, 
and  constitutes  Canton’s  phosphorus,  commonly  made  by 
igniting  oyster  shells  with  sulphur  ; possesses  the  curious 
quality  of  shining  in  the  dark,  after  a brief  exposure  to  the 
sun  or  to  the  rays  of  an  electric  spark. 

SALTS  OF  THE  PROTOXIDE  OF  CALCIUM. 

Carbonate  of  Lime  is  abundantly  found  in  nature,  form- 
ing whole  ranges  of  mountains,  the  limestones,  marbles, 
&c.,  of  mineralogists.  It  occurs  pure  in  the  form  of  Iceland 
spar,  in  rhomboidal  crystals,  possessed  of  double  refraction. 
It  is  dimorphous,  assuming  the  form  of  six-sided  prisms,  as 
in  the  mineral  called  Arragonite.  It  is  anhydrous,  insolu- 
ble in  water,  but  in  water  charged  with  carbonic  acid  it  is 
soluble,  and  is  deposited  from  such  a liquid  on  boiling,  or 
by  the  difiusion  of  carbonic  acid  into  the  air.  The  carbon- 
iq  acid  is  expelled  from  this  salt  by  a red  heat,  and  the  ac- 
tion of  the  more  powerful  acids.  Carbonate  of  lime  may 
be  obtained  in  union  with  water,  by  boiling  hydrate  of  lime 
with  a solution  of  sugar. 

For  what  purposes  is  the  chloride  of  calcium  used?  Under  what  forms 
does  fluoride  of  calcium  occur  ? What  singular  quality  does  the  sulphuret 
of  calcium  possess  ? What  are  the  dimorphous  forms  of  carbonate  of  lime  f 
Under  what  circumstances  is  it  soluble  in  water  ? 


MAGNESIUM. 


277 


Sulphate  of  Lime — Gypsum — occurs  native,  both  in 
crystals,  the  primary  form  being  a rhombic  prism,  and  also 
in  extensive  crystalline  masses.  It  contains  two  atoms  of 
water ; there  is  a variety,  however,  passing  under  the  name 
of  anhydrite,  which  contains  no  water.  On  calcining  the 
hydrous  sulphate  of  lime  at  a low  red  heat,  it  becomes  plas- 
ter of  Paris,  and  has  the  property  of  setting  into  a hard  mass 
when  made  into  a paste  with  water.  The  sulphate  of  lime 
is  soluble  in  500  parts  of  boiling  water,  and  often  occurs  in 
the  water  of  springs,  to  which  it  communicates  hardness. 

Phosphate  of  Lime — Bone-earth  Phosphate — is  one  of 
the  tribasic  phosphates  ; it  is  precipitated  when  earth  of 
bones  is  dissolved  in  muriatic  acid,  and  the  solution  neu- 
tralized by  ammonia. 

Chloride  of  Lime — Bleaching  Powder — is  made  by  ex- 
posing hydrate  of  lime  to  chlorine.  It  is  a white  powder, 
exhaling  a faint  odor  of  chlorine,  and  is  used  extensively  as 
a bleaching  agent. 

MAGNESIUM.  i»f^==12-7. 

Magnesium  may  be  procured  by  igniting  a mixture  of 
chloride  of  magnesium  and  sodium  in  a porcelain  crucible  ; 
the  chloride  of  sodium  forms,  and  magnesium  is  set  free. 
The  chloride  may  be  dissolved  by  water. 

It  is  a white,  malleable  metal,  which  melts  at  a red 
heat,  and,  with  excess  of  air,  oxydizes,  forming 

Protoxide  of  Magnesium.  MgO  = 20'713. 

This  substance,  called,  also,  calcined  magnesia,  or  sim- 
ply magnesia,  may  be  made  by  heating  the  carbonate  to 
low  redness  ; the  carbonic  acid  is  driven  off,  and  the  mag- 
nesia remains  as  a white  powder,  insoluble  in  water,  but 
neutralizing  acids  completely,  and  forming  with  them  a 
complete  series  of  salts. 

Magnesia  occurs  very  abundantly  in  nature,  often  asso- 
ciated as  a carbonate  with  carbonate  of  lime,  as  in  dolo- 
mitic  limestone.  It  also  occurs  in  fertile  soils,  and  is  essen- 
tial to  the  growth  of  certain  plants. 

It  is  well  distinguished  from  all  the  foregoing  alkaline 
earths  by  the  relation  of  its  sulphate.  The^  sulphates  of 

Under  what  forms  does  sulphate  of  lime  occur,  and  for  what  purpose  is  it 
used  ? In  what  does  the  phosphate  of  lime  occur  ? What  is  bleaching  pow- 
der ? How  is  magnesium  obtained  ? What  are  the  properties  of  it  ? Under 
what  names  does  the  protoxide  pass  ? What  is  dolomitic  limestone  ? 


m 


SALTS  OP  MAGNESIUM* 


baryta,  strontia,  and  lime  form  a series  of  salts,  the  solu- 
bility of  which,  in  water,  is  constantly  increasing  ; to  these 
the  corresponding  magnesia  salt  may  be  added  ; it  is  very 
soluble. 

Magnesia  is  precipitated  from  its  sulphate  by  the  caustic 
alkalies,  and  by  the  carbonates  of  potash  and  soda  as  a car- 
bonate, but  not  by  the  carbonate  of  ammonia  in  the  cold. 
It  may  be  detected  by  adding  carbonate  of  ammonia  and 
phosphate  of  soda  in  succession,  when  the  phosphate  of 
magnesia  and  ammonia  is  precipitated.  Heated  before  the 
blow-pipe,  after  having  been  moistened  with  nitrate  of  co- 
oalt,  magnesia  becomes  of  a pinkish  color. 

SALTS  OF  THE  PROTOXIDE  OF  MAGNESIUM. 

Carbonate  of  Magnesia  is  found  native,  and  may  be 
prepared  by  boiling  the  sulphate  with  an  alkaline  carbon- 
ate, diffusing  the  precipitate  in  water,  and  passing  a stream 
of  carbonic  acid  through  it ; by  spontaneous  evaporation, 
the  carbonate  of  magnesia  is  deposited  in  crystals.  The 
carbonate  of  magnesia,  the  magnesia  alba  of  the  shops,  is 
prepared  by  precipitating  the  sulphate  of  magnesia  with 
the  carbonate  of  potash  ; it  occurs  in  light  white  cubical 
cakes,  or  in  powder,  and  is  not  a true  carbonate,  for  it  does 
not  contain  a full  equivalent  of  carbonic  acid.  It  is  said  to 
be  a compound  of  one  atom  of  hydrate  of  magnesia  with 
three  atoms  of  hydrated  carbonate  of  magnesia.  It  is  very 
slightly  soluble  in  water. 

Sulphate  of  Magnesia — Epsom  Salts  of  commerce — is 
produced  by  the  action  of  dilute  sulphuric  acid  on  magne- 
sian limestone.  Its  crystals  are  small  four-sided  prisms, 
soluble  in  an  equal  weight  of  cold  and  three  fourths  their 
weight  of  boiling  water,  the  solution  having  a bitter  taste. 
A low  heat  expels  six  out  of  the  seven  equivalents  of  the 
combined  water. 

Phosphate  of  Magnesia  and  Ammonia^  one  of  the  va- 
rieties of  urinary  calculus,  may  be  formed  artificially  when 
a tribasic  phosphate,  a salt  of  ammonia,  and  a salt  of  mag- 
nesia are  mixed  together. 

Magnesium  is  the  last  of  the  alkaline  earthy  metals.  Its 
history  completes  that  of  our  first  group  of  metallic  bodies. 

How  may  magnesia  be  detected  ? How  is  its  carbonate  prepared  ? Of 
what  is  Epsom  salt  compose^  ? In  what  form  is  the  phosphate  of  magnesi* 
and  ammonia  sometimes  found  ? 


ALUMINUM.  279 

At  the  head  of  the  second  group  we  find  aluminum,  the 
first  of  the  earthy  metals. 

ALUMINUM.  AI=137. 

Obtained,  by  Wholer,  by  the  action  of  sodium  on  the  chlo* 
ride  of  aluminum,  being  the  same  process  as  that  given  for 
the  preceding  metal. 

It  is  a gray  powder,  which  melts  beneath  a red  heat ; 
takes  fire  when  heated  in  air,  producing 

Sesquioxide  of  Aluminum.  = 51*539. 

This  oxide,  called,  also,  alumina  and  clay,  occurs  nat* 
urally  under  certain  forms,  which  are  highly  prized,  as  the 
ruby  and  sapphire.  In  a more  impure  condition  it  yields 
the  various  common  clays,  which  also  contain  silica  or  me- 
tallic oxides,  or  other  extraneous  bodies. 

Alumina  may  be  prepared  from  the  sulphate  of  alumina 
and  potassa,  common  alum,  by  precipitating  the  sulphuric 
acid  by  chloride  of  barium.  The  sulphate  of  baryta  goes 
down,  and  there  is  left  in  the  solution  chloride  of  potassium 
and  chloride  of  aluminum.  When  the  mass  is  dried,  water 
is  decomposed ; hydrochloric  acid  is  then  expelled,  and 
alumina,  mixed  with  the  chloride  of  potassium,  remains  be- 
hind ; the  latter  is  to  be  dissolved  away  by  water,  leaving 
the  alumina  as  a white  substance,  which,  with  water,  forms 
a plastic  mass,  capable  of  being  moulded,  and  retaining  its 
shape  when  baked.  After  ignition,  it  adheres  to  the  tongue, 
and  during  the  act  of  drying  it  contracts  considerably  in 
volume,  a property  which  formerly  gave  rise  to  the  inven- 
tion of  Wedgewood’s  pyrometer. 

The  presence  of  alumina  gives  to  the  clays  those  proper- 
ties which  fit  them  for  the  purpose  of  the  potter  and  brick- 
maker.  Alumina  is  also  used  as  a mordant  to  fix  the  colors 
of  certain  dyes  upon  cloth. 

Alumina  is  precipitated  from  its  solutions  by  fixed  alka- 
lies, which  yield  a white  hydrate  of  alumina,  soluble  in  an 
excess  of  the  precipitant.  It  is  also  thrown  down  by  alka- 
line carbonates ; and,  when  these  precipitations  are  made 
in  a solution  tinged  with  coloring  matter,  the  alumina  car- 
ries it  down  with  it.  Such  colored  precipitates  pass  under 

How  is  aluminum  prepared?  What  is  the  constitution  of  its  oxide? 
Under  what  natural  forms  does  it  occur?  How  may  alumina  be  prepared? 
What  principle  is  involved  in  Wedgewood’s  pyrometer?  What  is  meant 
by  a mordant  ? How  may  the  presence  of  alumina  be  recognized  ? 


280 


PORCELAIN. EARTHEN-WARE. GLASS. 


the  name  of  lakes  ; and  it  is  this  property  of  attaching  such 
colors  to  itself,  enabling  it  to  cause  their  firm  adhesion  to 
cloth  fibre,  which  is  the  principle  of  its  application  as  a 
mordant. 

Among  the  purposes  to  which  alumina  is  applied  may  he 
mentioned  the  manufacture  of  Porcelain,  and  the  dificrent 
kinds  of  earthen- ware.  The  former  substance,  first  made 
by  the  Chinese,  is  very  compact  and  translucent.  It  con- 
sists essentially  of  clay  mixed  with  a fusible  body,  which 
binds  all  its  parts  together,  and  is  covered  with  a glaze, 
which  does  not  terminate  abruptly  on  the  surface,  but  per- 
vades the  substance  of  the  mass.  In  this  respect  it  differs 
from  common  earthen-ware.  Feldspar,  or  the  silicate  of 
lime,  are  bodies  suitable  for  communicating  this  glassy 
structure. 

. In  the  manufacture  of  porcelain,  great  care  is  taken  to 
select  clay  free  from  iron.  It  is  mixed  with  powdered  quartz 
and  feldspar,  and  the  requisite  shape  given  it  either  by  the 
potter’s  wheel,  or  by  pressing  it  into  moulds.  It  is  then 
dried  in  the  air,  and  more  perfectly  in  a furnace,  and,  when 
ignited,  forms  biscuit.  This  is  dipped  in  the  glaze,  sus- 
pended in  water,  and  becomes  covered  over  with  a uniform 
coat  of  it.  It  now  remains  to  dry  it  once  more,  and  fuse 
the  glaze  upon  it. 

Earthen-ware  consists  of  a white  clay  mixed  with  sil- 
ica. It  is  glazed  with  a fusible  material  containing  oxide 
of  lead,  and  colored  of  different  tints  by  metallic  oxides ; 
for  example,  blue  by  cobalt. 

Connected  with  the  manufacture  of  pottery  may  also  be 
mentioned  the  manufacture  of  Glass,  of  which  there  are 
several  varieties,  some  consisting  of  silica,  potash  or  soda, 
and  lime,  others  containing  a large  quantity  of  oxide  of  lead 
If  silica  be  heated  with  carbonate  of  potash  and  lime,  or 
oxide  of  lead,  carbonic  acid  is  expelled,  and  glass  forms. 
The  mass  is  kept  in  a fused  condition  till  it  is  free  from  air 
bubbles,  and  is  then  cooled  until  it  becomes  plastic,  so  that 
it  may  be  blown  or  moulded. 

Articles  of  glass,  after  they  are  manufactured,  require  to  be 
annealed  or  slowly  cooled  down.  This  allows  their  parts  to 
assume  a regular  structure,  and  prevents  excessive  brittle- 
ness. 


What  are  lakes  ? What  substances  are  used  in  the  preparation  of  por 
celain  and  earthen-ware  ? How  is  glass  made  ? Why  must  it  be  annealed 


SALTS  OF  ALUMINUM. 


281 


Soluble  glass  is  formed  when  silica  is  heated  with  twice 
its  weight  of  carbonate  of  soda  or  potash.  It  derives  its 
name  from  the  fact  that  it  is  for  the  most  part  soluble  in 
water. 


SALTS  OF  THE  SESQUIOXIDE  OF  ALUMINUM. 

Sulphate  of  Alumina  is  made  by  dissolving  alumina  in 
dilute  sulphuric  acid.  It  enters  into  the  composition  of  the 
alums. 

Sulphate  of  Mumina  and  Potash — Mum. — This  im- 
portant salt  is  prepared  from  alum  slate.  It  crystallizes  in 
octahedrons,  has  an  astringent  taste,  reddens  litmus  paper. 
It  dissolves  in  about  eighteen  times  its  weight  of  cold,  and 
less  than  its  own  weight  of  boiling  water.  It  contains 
twenty-four  atoms  of  water,  and,  when  exposed  to  heat, 
foams  up,  melting  in  its  own  water,  which,  being  evapora- 
ted away,  leaves  a white  porous  mass,  commonly  called 
burnt  alum. 

In  the  same  way  that  the  sulphate  of  potash  unites  with 
the  sulphate  of  alumina,  so  also  do  the  sulphates  of  am- 
monia and  of  soda,  forming  respectively  the  ammoniacal 
and  soda  alums.  The  alumina  in  the  common  alum  may 
be  replaced,  also,  by  the  sesquioxides  of  iron,  manganese,  or 
chromium,  giving  iron,  manganese,  and  chrome  alums. 

The  following  metals,  Glucinum,  Thorium,  Yttrium,  Zir- 
conium, Lanthanium,  and  Cerium,  are  very  rare  bodies,  and, 
being  of  little  interest,  may  be  passed  over  without  farther 
notice. 


LECTURE  LXI. 

Manganese. — Its  Seven  Oxides. — The  Peroxide  and  its 
Applications. — Mineral  Chameleon. — Acids  of  Manga- 
nese. — Salts  of  the  Protoxide.  — Iron.  — Its  Natural 
Forms. — Reduction  on  the  Great  Scale. — Cast  Iron. — 
Wrought  Iron. — Steel. — Passive  Iron. 

MANGANESE.  Mn=z  2T7. 

Manganese  may  be  procured  by  igniting  its  oxides  with 

What  are  the  properties  of  the  sulphate  of  alumina  and  potash  ? How 
may  manganese  be  obtained  ? What  are  its  properties  ? How  many  qx 
ides  does  it  furnish  ? How  may  manganese  be  detected  ? 


282 


MANGANESE. 


a mixture  of  lampblack  and  oil  in  a powerful  furnace,  the 
reduction  being  somewhat  difficult.  It  is  a white  metal, 
specific  gravity  8 0 13,  requiring  a white  heat  for  its  fusion, 
and  oxydizing  readily  in  the  air.  It  is  remarkable  for  the 
number  of  oxygen  compounds  which  it  yields ; they  are 
MnO  . . . Mn^O^ . . . MnO^  . . . MnO^  . . . Mn^O^ . . . 
Mn^O^  . . . 

designated  respectively. 


Protoxide  of  manganese. 
Sesquioxide  of  manganese. 
Peroxide  of  manganese. 
Manganic  acid. 


Permanganic  acid. 

Red  oxide  of  manganese. 
Varvicite. 


Of  these,  the  protoxide  may  be  made  by  passing  hydrogen 
gas  over  red-hot  peroxide  of  manganese.  It  is  of  a green 
color,  is  a basic  body,  and  forms  a series  of  salts,  of  which 
the  sulphate  is  used  in  dyeing.  It  is  isomorphous  with  mag- 
nesia and  zinc.  Hydrosulphuret  of  ammonia  yields  with  it 
a flesh-colored  precipitate,  ferrocyanide  of  potassium  a white, 
and  the  chloride  of  soda  a dark  brown  hydrated  peroxide. 
The  sesquioxide  is  made  by  igniting  the  peroxide,  as  will 
be  presently  explained.  The  red  oxide  and  varvicite  occur 
as  minerals ; but  of  the  whole  series  the  peroxide  is  by  far 
the  most  valuable. 


Peroxide  of  Manganese,  Mn Og  = 43-726, 
is  found  abundantly  as  a mineral,  and  passes  in  commerce 
under  the  name  of  black  oxide  of  manganese,  a name  indi- 
cating its  color.  It  is  insoluble  in  water,  and,  when  exposed 
to  a red  heat,  gives  off  one  fourth  of  its  oxygen,  forming  the 
sesquioxide,  as  stated  above,  the  action  being 
2(ilf^02)  Mn^O^  + O. 

On  this  fact  is  founded  one  of  the  processes  for  obtaining 
oxygen  gas.  Heated  with  hydrochloric  acid,  it  yields  chlo- 
rine, as  has  been  explained.  It  was  formerly  called  glass- 
makers’  soap,  from  the  circumstance  that  it  removes,  when 
added  to  melted  glass,  the  stain  of  protoxide  of  iron,  by  turn- 
ing it  into  peroxide,  and  causes  the  glass  to  become  color- 
less ; but  if  too  great  a proportion  of  peroxide  of  manganese 
is  used,  the  glass  assumes  an  amethystine  color. 

Peroxide  of  manganese,  when  ignited  with  caustic  potash 
in  a platina  crucible,  yields  a substance  known  as  Mineral, 


What  is  the  constitution  of  the  peroxide  ? What  color  does  it  give  t® 
glass  ? 


COMPOUNDS  OP  MANGANESE. 


283 


Chameleon i which  is  of  a green  color.  Water  dissolves 
from  it  the  Manganate  of  Potash,  which  is  of  a beautiful 
grass  green,  the  solution  speedily  passing  through  a variety 
of  shades  of  purples,  blues,  and  reds.  As  yet,  manganic 
acid  is  a hypothetical  compound,  and  has  not  been  insulated. 
When  mineral  chameleon  is  dissolved  in  hot  water,  a red 
solution  is  obtained  of  the  Permanganate  of  Potash  ; from 
the  permanganate  of  baryta  a crimson  solution  of  Perman- 
ganic Acid  may  be  procured  by  the  aid  of  sulphuric  acid  ; 
but  permanganic  acid  can  not  be  obtained  in  the  solid  form. 

Among  other  compounds  of  manganese,  the  following  may 
be  named  : 

Protochloride  of  manganese  MnCl  r=  63*15. 

Perchloride  “ “ Mn^Clj  = 303"  19. 

Perfluoride  “ “ Mn^Fl-j  = 186*46. 

The  protochloride  may  be  made  by  acting  on  the  peroxide 
with  muriatic  acid,  evaporating  to  dryness,  and  fusing  at  a 
red  heat.  On  digesting  with  water,  the  protochloride  dis- 
solves, and  any  impurity  of  iron  is  left  in  the  state  of  oxide. 
Then,  by  crystallizing,  the  chloride  can  be  obtained  in  pink 
crystals.  The  perchloride  is  produced  when  permanganate 
of  potash,  common  salt,  and  sulphuric  acid  are  heated.  It 
is  a dark  greenish  and  volatile  liquid.  The  perfluoride  is 
obtained  by  distilling  sulphuric  acid,  permanganate  of  pot- 
ash, and  fluor  spar  ; it  is  a greenish  yellow  gas. 

SALTS  OF  THE  PROTOXIDE  OF  MANGANESE. 

Protosulphate  of  Manganese,  formed  by  dissolving  prot- 
oxide of  manganese  in  sulphuric  acid.  The  figure  of  its 
crystals  depends  on  the  temperature  at  which  they  were 
formed.  They  have  a rose-colored  tint.  It  is  insoluble  in 
alcohol,  very  soluble  in  water,  and  is  used  by  the  dyers  to 
produce  a fine  brown  color. 

There  is  but  one  sulphuret  of  manganese.  It  is  obtained 
as  a hydrate  when  manganese  is  precipitated  by  hydrosul- 
phuret  of  ammonia  {MnS,  HO).  It  is  of  a flesh-red  color 

IRON.  Fe  = 28*00. 

Iron  sometimes  occurs  in  a native  state  and  as  meteoric 
iron,  also  as  oxide,  carbonate,  sulphuret,  &c.  It  is  one  of 

How  is  mineral  chameleon  made  ? What  are  its  properties  ? Can  man- 
ganic acid  be  isolated  ? How  may  the  chhirides  of  manganese  be  formed  ? 
What  are  the  properties  of  the  fluoride  ? What  is  the  formation  and  use  of 
the  protosulphate  of  manganese  ? 


284 


IRO^’ 


the  most  abundant  of  the  metals.  Much  of  what  is  found 
in  commerce  is  derived  from  clay  iron-stone,  which  is  an 
impure  carbonate  containing  silica,  alumina,  magnesia,  and 
other  foreign  substances.  The  native  peroxide  of  iron,  red 
haematite ; the  hydrated  peroxide,  brown  haematite  ; the 
black  oxide,  or  magnetic  iron  ore,  furnish  some  of  the  finer 
varieties  of  the  metal. 

From  clay  iron-stone  metallic  iron  is  procured  by  the  ac- 
tion of  carbonaceous  matter  and  lime  at  a high  temperature. 
The  ore,  having  been  roasted,  is  thrown  into  the  furnace 
with  coal  and  lime.  If  the  iron  is  in  the  ore  as  a silicate, 
the  lime  decomposes  it  at  those  high  temperatures,  forming 
a slag  of  silicate  of  lime,  and  the  oxide  of  iron  set  free  is 
instantly  reduced  by  the  carbonaceous  matter ; the  metal 
sinking  down,  protected  by  the  slag,  is  let  off  by  opening  a 
hole  in  the  bottom  of  the  furnace. 

The  substance  thus  produced  is  not  pure  iron  ; it  contains 
carbon  and  other  impurities,  and  passes  under  the  name  of 
cast  or  pig  iron.  It  is  purified  by  melting  and  sudden  cool-, 
ing,  which  converts  it  mto  fine  metal;  this  fine  metal  is 
then  melted  under  exposure  to  air,  which  burns  off  the  car- 
bon as  carbonic  oxide,  and  the  mass,  from  being  perfectly 
fluid,  becomes  coherent.  It  is  now  subjected  to  violent  me- 
chanical action,  such  as  hammering  or  rolling ; this  forces 
out  or  burns  off  the  impurities,  increases  its  tenacity,  and  it 
becomes  the  wrought  iron  of  commerce. 

Cast  Iron  melts  readily  at  a bright  red  heat,  and  ex- 
pands in  solidifying ; on  this  depends  its  valuable  applica- 
tion for  making  castings.  Kept  under  the  surface  of  salt 
water  for  a length  of  time,  cast  iron  becomes  converted  into 
a body  somewhat  like  plumbago,  due,  probably,  to  the  re- 
moval of  the  iron  as  a chloride  ; the  carbon  which  is  left 
behind  is  sometimes  observed,  as  it  dries,  to  become  hot  : a 
phenomenon  to  be  accounted  for  by  its  porous  state.  These 
facts  have  been  frequently  verified  in  the  case  of  cannon 
which  have  lain  for  years  at  the  bottom  of  the  sea.  There 
are  two  forms  of  cast  iron,  white  and  gray  ; the  former  con- 
tains about  five  per  cent,  of  carbon,  the  latter  three  or  four. 

Pure  Iron  may  be  obtained  by  decomposing  precipitated 
peroxide  of  iron  by  hydrogen  gas,  and  melting  the  result. 

What  are  the  forms  under  which  iron  chiefly  occurs?  How  is  it  obtain 
ed  from  clay  iron-stone  ? What  is  cast  iron  ? By  what  processes  is  it  con 
verted  into  wrought  iron?  What  are  the  properties  of  cast  iron?  Whal 
changes  does  it  undergo  under  water  ? How  may  pure  iron  be  obtained  1 


IRON. 


285 


The  metal  has  a bluish  color,  is  more  ductile  than  mallea- 
ble, and  is  the  most  tenacious  of  all  bodies.  It  becomes 
very  soft  at  a red  heat,  and  possesses  the  welding  proper- 
ty ; on  this  depends  the  art  of  forging  it.  Its  specific  grav- 
ity is  7*7.  It  is  one  of  the  few  magnetic  bodies,  and,  when 
soft,  its  magnetism  is  so  transient  that  it  may  gain  and  lose 
that  quality  a thousand  times  in  a minute.  The  melting 
point  of  iron  is  very  high.  In  the  mode  of  preparing  it  from 
cast  iron  it  does  not  undergo  the  process  of  fusion,  but  its 
particles  are  simply  welded  together.  The  fibrous  struc- 
ture which  wrought  iron  possesses  is  the  chief  cause  of  its 
great  tenacity  ; a wire  ^th  of  an  inch  in  diameter  will 
bear  a weight  of  60  pounds. 

Steel,  which  is  a valuable  preparation  of  iron,  is  made 
by.  placing  alternate  strata  of  iron  bars  and  charcoal  pow- 
der in  a close  box  and  keeping  them  red  hot.  The  process 
is  known  by  the  name  of  cementation.  The  iron  gains 
about  1'5  per  cent,  of  carbon.  Steel  is  much  more  fusible 
than  iron,  and  becomes  excessively  hard  and  brittle  by  being 
brought  to  a red  heat  and  then  suddenly  quenched  in  cold 
water.  When  allowed  to  cool  slowly,  it  is  quite  soft,  and 
various  degrees  of  elasticity  and  hardness  may  be  given  to 
it  by  the  process  of  tempering. 

By  placing  a piece  of  platina  in  nitric  acid  of  a specific 
gravity  of  194,  and  then  bringing  an  iron  wdre  in  contact 
with  it  and  withdrawing  the  platina,  the  iron  assumes  a 
passive  or  allotropic  state.  It  now  exhibits  no  tendency  to 
unite  with  oxygen,  can  not  precipitate  copper  from  its  solu- 
tions, and  simulates  the  properties  of  platina  and  gold. 


LECTURE  LXII. 

Iron. — Oxides  of. — Three  Oxides  and  Ferric  Acid. — 
Tests  for  Iron. — Salts  of  the  Protoxide  and  Peroxide. 
— The  Sidphurets. — Nickel. — Its  Peduction  from  the 
Oxalate.  — Cobalt. — Smalt.  — Zaffre. — S^jmpathetic 
Ink. — Zinc. — Distillation  of. — Salts  of  the  Protoxide. 

IRON  AND  OXYGEN. 

Iron  burns  with  rapidity  in  oxygen  gas,  as  may  be  proved 

\vnat  are  its  properties?  What  is  steel?  How  is  it  made,  and  what 
are  its  properties  ? How  may  iron  be  rendered  passive  ? 


286 


OXIDES  OF  IRON. 


Fi^.  269.  igniting  a piece  of  it  in  wire  coiled  into  a spiral 
form  in  a jar  of  that  gas  {Fig.  269),  when  it  will 
be  found  to  take  fire  and  burn  beautifully.  In  at- 
mospheric air,  under  favorable  circumstances,  the 
combustibility  of  this  metal  may  be  proved.  Thus, 
fine  iron  filings,  sprinkled  in  the  flame  of  a spirit 
lamp,  burn  with  scintillations  ; exposed  to  air  and 
moisture,  it  slowly  rusts.  Iron  yields  four  oxides  : 

Protoxide  ....  FeO  — 36'013. 

Black  oxide  . . . 7^6304  = 116'052. 

Peroxide  ....  Fe^O^  = 80  039. 

Ferric  acid  ....  . FeO^  = 52'039. 

Frotoxide  of  Iron.  jPeO  = 36*013. 

This  oxide  has  not  yet  been  insulated,  but  it  exists, 
united  with  acids,  in  an  extensive  series  of  salts,  from 
which  it  is  thrown  down  as  a hydrate  by  alkalies,  and  is 
then  of  a white  color,  which  darkens  as  it  passes  into  the 
state  of  peroxide.  Ferrocyanide  of  potassium  gives  a white 
precipitate,  and  the  ferridcyanide  a deep  blue.  Hydrosul- 
phuret  of  ammonia  gives  a black  sulphuret  of  iron.  Sul- 
phureted  hydrogen  and  gallic  acid  give  no  precipitate. 

Black  Oxide  of  Iron.  jP^gO^  =116*052. 

This  oxide,  known  also  as  the  magnet  or  loadstone,  is 
found  as  a mineral.  It  is  a compound  of  the  protoxide  and 
peroxide.  The  scales  of  iron  found  in  blacksmiths’  forges 
mainly  consist  of  it.  It  may  also  be  produced  by  decom- 
posing the  vapor  of  water  by  metallic  iron  in  a red-hot  tube. 

Peroxide  of  Iron,  FefO.^  = 80*039, 
is  found  in  nature  as  oligist  iron,  or  as  a hydrate.  , It  may 
be  produced  artificially  as  a hydrate  by  precipitation  from  a 
solution  of  persulphate  of  iron  by  a caustic  or  carbonated 
alkali,  or  in  a pure  state  by  igniting  green  vitriol  ; there  is 
then  left  a red  powder,  known  as  rouge,  used  for  polishing 
metals.  This  oxide  is  not  magnetic;  it  is  the  basis  of  a 
series  of  salts  which  yield,  with  alkalies,  a brown  hydrated 
peroxide  ; with  ferrocyanide  of  potassium,  Prussian  blue  ; 

How  may  the  rapid  oxydation  of  iron  be  illustrated  ? How  many,  oxides 
does  this  metal  yield  ? What  are  the  reactions  which  the  protoxide  fur- 
nishes with  tests  ? Under  what  natural  forms  does  the  black  oxide  occur? 
How  may  it  be  formed  artificially  ? What  are  the  natural  forms  of  the  per- 
oxide ? How  may  it  be  prepared  ? For  what  purposes  is  it  used  ? What 
is  its  action  with  reagents  ? 


OXIDES  OF  IRON. 


287 


with  sulphocyanide  of  potassium,  a blood-red  solution ; with 
wannin  and  gallic  acid,  a black.  This  last  is  of  considerable 
interest,  constituting  the  basis  of  ordinary  ink. 

The  presence  of  iron  can  always  be  determined  by  pass- 
ing it  into  the  condition  of  peroxide,  and  applying  the  fore- 
going tests. 

Ferric  Acid,  JPeOg  = 52*039, 
is  prepared  by  heating  peroxide  of  iron  with  four  parts  of 
nitrate  of  potash.  The  result  is  treated  with  cold  water, 
which  yields  a red  solution  of  the  ferrate  of  potash.  This 
slowly  decomposes  in  the  cold,  and  very  rapidly  when  the 
solution  is  warm.  The  ferrate  of  baryta  precipitates  when 
the  potash  solution  is  acted  on  by  a soluble  salt  of  baryta. 
It  is  a permanent  body,  of  a crimson  color. 

Among  other  compounds  of  iron,  the  following  may  be 
named : 


Protochloride  of  iron  . . . 

. . . FeCl 

= 63*47 

Perchloride  “ . . . 

= 162*35 

Protiodide  “ . . . 

= 153*57 

Protosulphuret  “ . . . 

. . . FeS 

= 44*12 

Sesquisulphuret  “ . . . 

= 104*36 

Bisulphuret  “ . . . 

. . . FeS^ 

= 60*24 

Of  these,  the  protochloride  is  formed  by  passing  hydrochlo- 
ric acid  over  red-hot  iron.  It  is  white,  but  forms  a green  so- 
lution in  water.  The  perchloride,  in  solution,  by  dissolving 
peroxide  of  iron  in  hydrochloric  acid.  The  protiodide,  by 
boiling  an  excess  of  iron  filings  with  iodine,  and  evapora- 
ting; it  forms,  on  cooling,  a dark  gray  mass.  Its  solution 
absorbs  oxygen  from  the  air.  The  protosulphuret  of  iron, 
which  is  much  used  for  forming  sulphureted  hydrogen,  may 
be  made  by  heating  a mass  of  iron  to  a white  heat,  and  ap- 
plying to  it  roll  sulphur,  and  receiving  the  melted  globules 
in  a bucket  of  water.  It  may  also  be  procured  by  igniting 
iron  filings  with  sulphur.  The  bisulphuret  occurs  abun- 
dantly as  a mineral  of  a golden  yellow  color,  crystallized  in 
cubes  or  allied  forms,  and  known  as  Iron  Pyrites.  It  fre- 
quently assumes  the  form  of  various  organic  remains,  being 
one  of  the  common  petrifying  agents,  but  in  this  state  differs 
essentially  from  the  cubic  pyrites,  both  in  color  and  oxydiz- 
ability,  these  fossil  remains  rapidly  decaying  under  exposure 

What  is  common  ink?  How  may  the  presence  of  iron  be  detected? 
What  are  the  properties  of  ferric  acid?  Of  the  other  compounds,  mention 
some  of  interest.  What  is  iron  pyrites  ? What  is  the  difference  of  its 
forms  ? 


288 


SALTS  OF  IRON. NICKEL. 


to  the  air,  but  the  other  form  being  unacted  on.  Besides 
these,  there  is  a sulphuret  of  iron  which  is  magnetic. 

SALTS  OF  THE  PROTOXIDE  OF  IRON. 

Carbonate  of  Iron  may  be  obtained  from  the  sulphate 
by  an  alkaline  carbonate,  falling  as  a whitish  precipitate. 
It  turns  brown,  however,  from  the  absorption  of  oxygen.  It 
occurs  as  a mineral  in  spathic  iron,  and  dissolves  in  water 
containing  carbonic  acid,  forming  chalybeate  waters. 

Protosuljphate  of  Iron — Copperas — Green  Vitriol — is 
prepared  largely  by  the  oxydation  of  iron  pyrites,  and  crys- 
tallizes in  oblique  prisms  of  a grass-green  color.  It  has  a 
styptic  taste,  dissolves  in  twice  its  weight  of  cold,  and  three 
fourths  its  weight  of  boiling  water.  It  contains  five  atoms 
of  water.  At  a low  red  heat  it  becomes  anhydrous.  In 
this  state  it  is  used  for  the  manufacture  of  the  Nordhausen 
sulphuric  acid. 

SALTS  OF  THE  PEROXIDE  OF  IRON. 

Persulphate  of  Iron  may  be  formed  by  adding  to  a so- 
lution of  the  protosulphate  of  iron  half  an  equivalent  of  sul- 
phuric acid,  and  peroxydizing  by  nitric  acid.  With  water 
it  forms  a red  solution. 

NICKEL.  iVi  = 29-5. 

Nickel  may  be  obtained  by  igniting  its  oxalate  in  a cov- 
ered crucible,  carbonic  acid  escaping,  and  the  metal  being 
reduced. 

NiO  + C2O3  ...  = ...  iW  + 2(002) ; 
one  atom  of  the  oxalate  of  nickel  yielding  one  of  the  metal 
and  two  of  carbonic  acid  gas. 

Nickel  is  a white  metal,  requiring  a high  temperature 
for  fusion.  It  is  magnetic,  and  has  a specific  gravity  of 
8*5.  It  is  commonly  associated  with  iron  in  meteorites,  and 
enters  into  the  composition  of  German  silver ; unites  with 
oxygen,  forming  a protoxide  and  sesquioxide,  the  former  yield- 
ing salts  of  a green  color  ; the  latter  is  an  indifferent  body. 

SALTS  OF  THE  PROTOXIDE  OF  NICKEL. 

Sulphate  of  Nickel  crystallizes  from  its  solutions  with  six 
atoms  of  water  in  slender  green  prisms,  which,  when  ex- 

How  is  carbonate  of  iron  formed  ? What  is  the  process  for  preparing  the 
sulphate  ? How  is  the  persulphate  obtained  ? By  what  process  is  nickel 
obtained  ? What  are  its  properties  ? Under  what  remarkable  circumstan 
ces  does  it  occur  with  iron  ? 


COBALT. ZINC. 


289 


posed  to  the  sun,  change  into  an  aggregate  of  octahedrons, 
becoming  opaque. 

Nickel  is  chiefly  used  in  the  preparation  of  German  sil- 
ver, an  alloy  of  copper,  zinc,  and  nickel.  It  is  of  a white 
color,  takes  a good  polish,  and  is  malleable. 

COBALT,  Co  = 20-5, 

is  generally  associated  with  iron  and  nickel,  and  Aviih  tliei  > 
occurs  in  meteoric  iron.  Like  the  preceding  metal,  it  iini}’ 
be  obtained  by  igniting  its  oxalate  in  a covered  crucible, 
carbonic  acid  being  disengaged  and  metallic  cobalt  left.  It 
is  a pinkish  white  metal,  requiring  a high  temperature  for 
fusion.  Its  specific  gravity  is  7 *8.  It  is  magnetic,  as  re- 
cent experiments  have  proved.  It  forms  a protoxide  and 
a sesquioxide,  the  former  being  the  basis  of  a class  of  salts 
which  are  chiefly  of  a pink  or  blue  color.  Smalt  is  a sili- 
cate of  cobalt,  and  Zaffre  an  impure  oxide ; the  former  is 
used  to  communicate  to  paper  a faint  blue  tinge,  and  the 
blue  color  which  the  oxide  gives  to  glass  is  taken  advantage 
of  in  coloring  the  common  varieties  of  earthen-ware.  Co- 
balt is  easily  detected  upon  this  principle. 

The  chloride  of  cobalt  may  be  made  by  dissolving  the 
oxide  or  the  metal  in  hydrochloric  acid.  It  is  a pink  solu- 
tion, which  turns  blue  when  dried.  It  forms  a beautiful 
sympathetic  ink^  for  letters  written  with  it,  especially  on 
paper  which  has  a pinkish  tinge,  are  entirely  invisible"^  but 
become  of  a bright  blue  color  when  the  paper  is  warmed, 
the  letters  again  fading  as  they  become  cool  and  moist. 

ZINC.  Zn  = 32-3. 

Zinc  is  a very  abundant  metal,  immense  quan- 
tities  of  it  occurring  in  the  state  of  New  Jersey 
and  in  various  other  places.  From  zinc  blende, 
which  is  a sulphuret,  converted  by  roasting  into 
an  oxide,  or  from  the  carbonate  brought  into  the 
same  state  by  ignition,  the  metal  may  be  obtained 
by  the  process  of  distillation  by  descent.  The 
oxide,  mixed  with  charcoal,  is  introduced  into  a 
crucible  which  has  an  iron  tube  passing  through 
a hole  in  its  bottom,  as  seen  in  Fig.  270,  and  the 

What  change  does  the  sulphate  of  nickel  undergo  in  the  sunlight  ? How 
is  cobalt  procured  ? Is  it  magnetic  like  nickel  ? What  is  smalt  ? What 
is  zaffre  ? What  arc  the  uses  of  cobalt  ? What  property  does  the  chloride 
possess  ? By  what  process  is  zinc  obtained  ? 

N 


290 


zoro. 


lid  being  luted  on,  tbe  temperature  is  raised  to  a white  heat, 
and  the  zinc,  distilling  over,  may  be  condensed  in  water. 

Zine  is  a bluish- white  metal,  which  melts  at  about  770® 
F.,  and,  if  exposed  at  a bright  red  heat  to  the  air,  takes 
fire  and  burns  with  a brilliant  pale  green  flame.  Its  spe- 
cific gravity  is  about  7*00.  At  common  temperatures  it  is 
brittle,  but  it  may  be  rolled  into  thin  sheets  at  about  300^ 
F.,  and  then  retains  its  malleability  when  cold.  During  its 
combustion  there  arises  from  it  a great  quantity  of  flocculent 
oxide,  which  formerly  went  under  the  name  of  nihil  cdhum, 
or  philosopher’s  wool.  Among  the  compounds  of  zinc  may 
be  mentioned 

Protoxide  of  zi;BC ZnO  = 40*313. 

Chloride  « ...... 

Sulphuret  **  ZnS  =48*4. 

Of  these,  the  oxide  is  formed,  as  has  been  said,  during 
the  combustion  of  zinc.  It  is  also  precipitated  as  a white 
hydrate  from  its  soluble  salts  by  potash  or  soda,  soluble  in 
excess  of  the  precipitant.  The  chloride  may  be  made  by 
the  action  of  hydrochloric  acid  on  metallic  zinc.  It  is  used 
in  the  arts  for  soldering  under  the  name  of  butter  of  zinc. 
The  sulphuret  occurs  as  a mineral  under  the  name  of  zinc 
blende. 

SALTS  OF  THE  PROTOXIDE  OF  ZINC. 

Sulphate  of  Zinc — White  Vitriol. — This  salt  is  formed 
in  the  process  for  procuring  hydrogen  gas  by  the  action  of 
dilute  sulphuric  acid  on  zinc.  It  crystallizes  in  colorless 
prisms  with  six  atoms  of  water,  and  is  soluble  in  two  and  a 
half  parts  of  cold  water.  It  has  a styptic  taste,  and  red- 
dens vegetables  blues.  There  are  three  different  subsul- 
phates of  this  oxide. 

Silicate  of  Zinc,  the  electric  calamine  of  mineralogists; 
remarkable  for  becoming  electric  when  heated. 

Is  there  any  connection  between  tbe  ductility  of  zinc  and  its  temperature? 
During  combustion,  what  arises  from  it  ? How  may  it  be  detected  ? How 
is  white  vitriol  prepared  ? What  is  electric  calamine  ? 


CADMIUM. TIN. 


291 


LECTURE  LXIII. 

Cadmium. — Sources  of. — Its  Volatility. — Tin. — Block  and 

Grain. — Its  Properties. — Protoxide  and  Stannic  Acid. 

— Chlorides  of  Tin.  — Mosaic  Gold.  — Its  Uses. — 

Chromium. — Chromiron. — Green  Oxide  and  its  Uses. 

— Chromic  Acid. — Salts  of  the  Sesquioxide. — Salts  of 

Chromic  Acid. — Other  Metals. — Titanium. 

CADMIUM.  Cd=zbhQ. 

Cadmium  usually  occurs  associated  with  zinc  as  a carbon- 
ate. In  the  preparation  of  that  metal  by  distillation,  as  has 
been  described.,  the  cadmium  first  comes  over.  From  any 
impurity  of  zinc  it  may  he  separated  by  precipitation  from 
an  acid  solution  by  sulphureted  hydrogen,  which  throws  the 
cadmium  down  as  a yellow  powder,  but  does  not  act  on  the 
zinc.  The  sulphuret  of  cadmium  is  then  dissolved  in  nitric 
acid,  the  oxide  precipitated  by  potash,  and,  when  dry,  re- 
duced by  charcoal.  The  compounds  of  cadmium  are  not 
important.  The  metal  itself  is  very  volatile. 

TIN.  Sn  = 5T9. 

Tin  occurs  as  an  oxide  in  England,  Mexico,  Germany,  and 
the  East  Indies.  It  may  he  reduced  by  the  action  of  char- 
coal at  a high  temperature.  It  is  found  in  commerce  under 
two  forms,  block  tin  and  grain  tin.  If  a bar  of  tin  is  heated, 
the  purer  parts,  being  the  more  fusible,  ooze  out  of  it,  con- 
stituting grain  tin,  and  the  mass  which  is  left  behind  is 
block  tin. 

Tin  is  a white  metal  like  silver.  It  oxydizes  in  the  air 
superficially,  the  action  ceasing  as  soon  as  a thin  crust  is 
formed.  At  a red  heat  it  oxydizes  rapidly,  forming  putty 
powder,  used  for  polishing  metals.  It  is  very  malleable, 
and  may  be  rolled  into  thin  foil.  When  bent  backward  and 
forward  it  emits  a crackling  sound.  It  is  very  soft ; its 
specific  gravity  7*2.  It  melts  at  442^,  and  burns  when 
raised  to  a high  temperature  in  the  air.  Some  of  its  com- 
pounds are 

Under  what  circumstances  does  cadmium  occur?  What  are  the  native 
forms  of  tin  ? What  are  block  and  grain  tin  ? What  are  the  properties  of 
tin  ? When  a bar  of  tin  is  bent  backward  and  forward,  what  phenomenon 
arises  ? 


292 


COMPOUNDS  OF  TIN. 


Protoxide  of  tin SnO  — 65*913. 

Sesquioxide  = 129*839. 

Peroxide SnO^  = 73*926. 

Protochloride SnCl  = 93*37. 

Perchloride SnCl^i  = 128*74. 

Protosulphuret SnS  = 7^' 

Persulphuret SnS2  = 90*1. 

The  protoxide  may  be  made  by  precipitation  from  the 
protochloride  by  carbonate  of  potash.  It  is  to  be  washed 
with  warm  water,  and  its  water  finally  driven  off  in  a cur- 
rent of  carbonic  acid  gas  at  a red  heat.  It  is  of  a black 
color,  is  easily  set  on  fire  in  atmospheric  air,  passing  into  the 
condition  of  peroxide.  Its  salts  reduce  the  noble  metals  to 
the  metallic  state,  when  added  to  their  solutions,  and  yield 
with  the  chloride  of  gold  the  Purple  of  Cassius.  The  per- 
oxide, called  also  stannic  acid,  from  exhibiting  weak  acid 
properties,  may  be  made  by  the  action  of  nitric  acid  on  tin. 
It  is  a hydrate  in  the  form  of  a white  powder,  insoluble  in 
acids  and  wate*r  ; but  if  obtained  by  precipitation  from  per- 
chloride of  tin,  it  is  soluble  both  in  acids  and  alkalies. 
Melted  with  glass,  it  forms  a white  enamel. 

The  protochloride  may  be  made  by  dissolving  tin  in  warm 
hydrochloric  acid.  The  solution,  when  concentrated,  depos- 
its crystals  of  the  hydrated  potochloride.  These  are  decom- 
posed when  heated.  The  anhydrous  protochloride  may  be 
had  by  passing  hydrochloric  acid  gas  over  metallic  tin  at  a 
red  heat.  The  perchloride  is  procured  by  distilling  eight 
parts  of  tin  with  twenty-four  of  corrosive  sublimate.  It  is 
a smoking  fluid,  and  was  formerly  called  the  Fuming  Li- 
quor of  Libavius.  A solution  of  this  substance,  much  used 
in  dyeing,  is  made  by  dissolving  tin  in  nitro-muriatic  acid, 
or  by  warming  a solution  of  the  protochloride  with  a little 
nitric  acid. 

..Of  the  sulphurets,  the  first  may  be  formed  by  pouring 
melted  tin  on  sulphur,  and  igniting  the  powdered  result 
with  more  sulphur  in  a crucible.  It  is  a bluish  gray  com- 
pound. The  persulphuret  is  obtained  when  two  parts  of 
peroxide  of  tin,  two  of  sulphur,  and  one  of  sal  ammoniac 
are  ignited  in  a retort.  It  is  a body  of  a golden  yellow  col- 
or, formerly  called  Aurum  Musivum,  or  Mosaic  gold,  in 
small  scales  of  a greasy  feel,  and  is  used  for  exciting  elec- 

How  is  the  protoxide  made,  and  how  do  its  salts  act  on  those  of  the  noble 
metals  ? How  is  stannic  acid  prepared  ? What  does  it  yield  with  glass  ? 
What  is  the  fuming  liquor  of  Libavius  ? How  is  mosaic  gold  made,  and 
what  is  its  use  ? 


CHROMIUM. 


293 


trical  machines,  being  much  more  energetic  than  the  com- 
mon amalgam,  though  less  durable  in  its  power. 

Tin  furnishes  several  valuable  metallic  combinations : 
Tin  Plate  is  sheet  iron  superficially  alloyed  with  it.  The 
soft  solders  are  alloys  of  lead  and  tin.  Pewter  is  an  alloy 
with  antimony. 

CHROMIUM.  Cr  = 28. 

Chromium  occurs  abundantly  near  Baltimore  as  the  chro- 
mate of  iron  {Chrome  Iron)^  more  rarely  as  the  red  chro- 
mate of  lead.  The  metal  may  be  obtained  by  the  action 
of  charcoal  on  the  oxide  at  a high  temperature,  and  is  of  a 
yellowish- white  color.  It  takes  its  name  from  its  tendency 
to  produce  highly  colored  compounds.  It  is  very  infusible, 
and  has  a specific  gravity  of  about  6 00.  Its  compounds, 
to  be  here  described,  are 

Sesquioxide  of  chromium  ....  Cr^O^  = 80'039. 

Chromic  acid CrO^  z=z  52  039. 

Sesquichloride  of  chromium  . . . Cr^Cl^  = 162  26. 

The  sesquioxide  may  be  prepared  by  heating  the  chro- 
mate of  mercury  to  redness  in  a crucible.  The  mercury  is 
driven  off,  and  the  chromic  acid  partially  deoxydized,  leav- 
ing a beautiful  grass-green  powder,  the  sesquioxide.  It 
may  also  be  obtained  by  heating  the  bichromate  of  potash 
red  hot,  and  washing  the  residue  in  water  ; also  as  a hy- 
drate, by  boiling  a solution  of  bichromate  of  potash  with 
muriatic  acid,  and  adding  alcohol ; the  mixture  becomes 
of  a green  color,  and  ammonia  precipitates  the  hydrated  ses- 
quioxide. It  is  a weak  base,  yielding  a class  of  salts  of  a 
blue  or  green  color.  In  the  state  of  hydrate  it  is  soluble 
in  acids ; but,  on  making  it  red  hot,  it  suddenly  becomes 
incandescent,  passes  into  another  allotropic  state,  and  is  now 
insoluble.  This  sesquioxide  is  isomorphous  with  the  ses- 
quioxides  of  iron  and  alumina.  In  its  two  allotropic  states 
it  yields  corresponding  classes  of  salts,  one  of  which  is  green, 
and  the  other  reddish  green.  It  is  used  for  communicating 
a green  color  to  porcelain. 

Chromic  Acid  may  be  made  by  adding  one  volume  of  a 
saturated  solution  of  bichromate  of  potash  to  one  and  a half 
of  oil  of  vitriol.  On  cooling,  red  crystals  of  chromic  acid 
are  deposited.  It  is  isomorphous  with  sulphuric  acid,  pro- 

What  alloys  does  tin  furnish  ? Under  what  forms  does  chromium  occuy 
in  nature  ? How  is  its  sesquioxide  prepared,  and  what  is  its  use  ? How 
is  chromic  acid  made  ? 


294 


COMPOUNDS  OP  CHROMIUM. 


duces  with  bases  yellow  and  red  salts,  is  a powerful  oxy- 
dizing  agent,  is  decomposed  by  a red  heat  into  the  sesquiox 
ide,  destroys  the  color  of  indigo  and  other  dyes,  and  may  be 
detected  by  producing  with  the  salts  of  lead,  chrome  yellow, 
and  by  its  ready  passage,  under  the  influence  of  deoxydiz 
ing  agents,  into  the  sesquioxide. 

The  sesquichloride  is  procured  when  chlorine  is  passed 
over  a mixture  of  the  sesquioxide  and  charcoal  in  a red- 
hot  tube.  It  is  a lilac-colored  body,  which  forms  a green 
solution  in  water.  There  is  also  an  oxychloride,  which  may 
be  distilled  as  a deep-red  liquid  from  a mixture  of  chromate 
of  potash,  common  salt,  and  oil  of  vitriol.  The  fluoride, 
which  is  a red  gas,  is  obtained  by  distilling  in  a silver  re- 
tort a mixture  of  chromate  of  lead,  fluor  spar,  and  oil  of 
vitriol.  It  is  decomposed  by  the  moisture  of  the  air,  form- 
ing chromic  and  hydrofluoric  acids. 

SALTS  OF  THE  SESQUIOXIDE  OF  CHROMIUM. 

Sulphate  of  Chromium  and  Potash — Chrome  Alum, 
— When  the  oxide  of  chromium  is  dissolved  in  sulphuric 
acid,  and  mixed  with  the  sulphate  of  potash  and  a little 
free  sulphuric  acid,  crystals  of  chrome  alum  are  deposited 
in  red  or  blue  octahedrons.  The  sulphate  of  chromium 
alone  does  not  crystallize. 

Chrome  Iron,  a compound  of  the  sesquioxide  of  chro- 
mium and  the  protoxide  of  iron,  is  found  native,  crystal- 
lized in  octahedrons,  and  also  massive.  It  furnishes  most 
of  the  compounds  of  chromium. 

SALTS  OF  CHROMIC  ACID. 

Chromate  of  Potash  may  be  made  by  igniting  chrome 
iron  with  one  fifth  its  weight  of  nitrate  of  potash.  It  crys- 
tallizes in  small,  lemon-yellow  prisms,  and  is  very  soluble 
in  hot  water.  The  crystals  are  anhydrous. 

Bichromate  of  Potash  may  be  prepared  from  the  former 
by  adding  an  equivalent  of  acetic  acid  : it  crystallizes  in 
prisms  of  a ruby  red.  Large  quantities  are  consumed  by 
dyers. 

Chromate  of  Bead-^  Chrome  Yellow,  obtained  by  pre- 

Does  chromic  acid  possess  bleaching  powers?  How  are  the  chloride 
and  fluoride  obtained  ? What  is  the  form  of  the  latter  body  ? What  ia 
chrome  alum  ? What  is  the  constitution  of  the  two  chromates  of  potash  ? 
What  is  chrome  yellow  ? 


ARSENIC.  295 

cipitation.  from  either  of  the  foregoing  salts  by  a soluble  salt 
of  lead.  It  is  used  as  a paint. 

Dichromate  of  Lead  is  formed  by  adding  chromate  of 
lead  to  melted  nitrate  of  potash,  and  dissolving  out  the 
chromate  of  potash  and  excess  of  nitre  by  water.  It  is  of 
a beautiful  red  color. 

The  following  metals,  Vanadium,  Tungsten,  Molybde- 
num, Osmium,  and  Columbium,  are  not  applied  to  any  pur- 
poses in  the  arts,  or  are  so  rare  as  not  to  be  of  general  in- 
terest. Titanium  might  be  included  in  the  same  observa- 
tion ; it  is,  however,  deserving  of  remark,  as  being  a red 
metal  like  copper,  and  titanie  acid,  one  of  its  oxygen  com- 
pounds, is  used  in  the  coloring  of  artificial  teeth. 


LECTURE  LXIV. 

Arsenic. — Preparation  of  the  Metal, — Properties  of  Ar- 
senious  Acid, — Two  Varieties  of  it, — Two  methods  of 
detecting  it. — Process  in  Cases  of  Poisoning. — Sul- 
phureted  Hydrogen  Test, — Marshs  Test. — The  Cop- 
per Test, — Difficulties  arising  from  Antimony. 

ARSENIC.  As=iZl'l, 

Arsenic  is  obtained  by  sublimation  in  a current  of  air 
of  the  arseniuret  of  cobalt  and  iron,  the  vapor  condensing 
as  a white  oxide.  This  being  mixed  with  powdered  char- 
coal or  black  flux,  and  heated,  the  metallic  arsenic  mg.  271, 
sublimes.  The  process  may  be  conducted  in  a tall 
vial  imbedded  in  a crucible  filled  with  sand,  two 
thirds  of  the  vial  projecting  above  the  heated  sand. 

On  this  cooler  portion  the  metal  condenses.  It  is 
also  sometimes  found  in  a native  state. 

Arsenic  is  a metallic  body,  of  an  aspect  darker  than  cast 
iron  ; it  is  very  brittle,  its  specific  gravity  is  5*88,  and, 
when  slowly  sublimed,  it  crystallizes  in  rhombohedrons.  At 
356°  P.  it  sublimes  without  undergoing  fusion,  its  melting 
point  being  much  higher  than  that  of  sublimation.  Its  va- 
por has  a smell  of  garlic,  as  may  be  readily  recognized  by 

What  is  the  color  of  titanium  ? From  what  substances,  and  in  what 
manner,  is  arsenious  acid  prepared  ? How  is  the  metal  obtained  from  it  T 
What  are  its  properties  ? Why  can  not  it  be  melted  ? What  is  the  odoi 
of  its  vapor  ? 


296 


COMPOUNDS  OF  ARSENIC. 


throwing  a little  arsenious  acid  on  a red-hot  coal.  Arsenic 
prepared  by  black  flux  tarnishes,  it  is  said,  from  containing 
a little  potassium.  Among  its  compounds,  the  following 
may  be  mentioned  : 


Arsenious  acid 

Arsenic  acid 

Protosulphuret  of  arsenic  . 
Sesquisulphuret  of  arsenic 
Arseniureted  hydrogen  . . 


. As^O^—  99*439. 
. 115*465. 

. AsS  = 53*8. 

As^S^  =z  123*7. 

AsH  z=  38*7. 


A-Tseuious  Acid  is  formed  when  arsenic  is  sublimed  in 
atmospheric  air.  It  is  a white  substance,  which,  when  the 
process  is  conducted  slowly,  crystallizes  in  octahedrons. 
Similar  octahedral  crystals  may  be  obtained  by  heating  ar- 
senious acid  itself  in  a tube  to  380°  F.  When  the  opera- 
tion has  been  recently  performed  and  a large  mass  sublimed, 
it  IS  a glassy,  transparent  body,  which  in  the  course  of  time 
slowly  becomes  milk-white.  The  specific  gravity  of  arse- 
nious acid  is  3-7.  It  is  nearly  tasteless,  of  sparing  solubility 
m water,  the  two  varieties  differing  in  this  respect.  By 
100  parts  of  water,  11*5  of  the  opaque,  but  only  9*7  of  the 
transparent,  are  dissolved.  This  substance  passes  cur- 
rently under  the  name  of  arsenic.  It  ought  not  to  be  for- 
gotten that  the  arsenic  of  chemical  writers  and  that  of 
commerce  are  very  different  bodies  : the  one  is  black  and 
the  other  white  ; the  one  is  a metal  and  the  other  its  oxide. 

Arsenious  acid  may  be  detected  by  several  methods  : 

1st.  W^ith  ammonia  sulphate  of  copper,  it  gives  an  em- 
erald green  precipitate  ; the  arsenite  of  copper,  or  Scheele’s 
green. 

2d.  With  the  ammonia  nitrate  of  silver,  a canary  yellow 
precipitate  ; the  arsenite  of  silver. 

3d.  With  sulphureted  hydrogen,  a solution,  previously 
acidulated  with,  acetic  or  muriatic  acid,  yields  a yellow  pre- 
cipitate, the  sesquisulphuret  of  arsenic,  orpiment  This 
when  dried  and  ignited  with  black  flux  (a  mixture' of  char- 
coal  and  carbonate  of  potash,  obtained  by  igniting  cream  of 
tartar  in  a covered  crucible),  yields  a sublimate  of  metallic 
arsenic. 


From  the  metal,  how  may  arsenious  acid  be  procured  ? What  change 
does  the  glassy  variety  underp  in  time  ? Of  these  varieties,  which  is  molt 
water?  What  is  the  difference  between  the  arsenic  of  chemists 
and  the  arsenic  of  commerce  ? What  is  the  action  of  ammonia  sulphate  of 
cppp  on  arspious  acid  ? What  of  the  ammonia  nitrate  of  silver''  What 
of  sulphureted  hydrogen  ? 


TESTS  FOR  ARSENIC. 


297 


4th.  With  the  materials  for  generating  hydrogen  gas ; 
that  is,  sulphuric  acid,  zinc,  and  water,  placed  in  a bottle ; 
if  arsenious  acid  be  present,  arseniureted  hydrogen  is  disen- 
gaged. When  set  on  fire,  it  burns  with  a pale  blue  flame, 
emitting  a white  smoke  ; and  if  a piece  of  cold  glass  be 
held  in  the  flame,  there  is  deposited  upon  it  a black  spot 
of  arsenic,  surrounded  by  a white  border  of  arsenious  acid. 
This  stain  is  volatilized  on  heating  the  glass.  Or  if  the  ar- 
seniureted hydrogen  be  conducted  through  a tube  of  Bohe- 
mian glass,  made  red  hot  at  one  point  by  a spirit  lamp,  it  is 
decomposed,  and  metallic  arsenic  deposited  on  the  cooler 
portions  beyond  the  ignited  space. 

5th.  If  a solution  containing  arsenious  acid  be  acidulated 
with  hydrochloric  acid,  and  boiled  with  slips  of  copper,  the 
metallic  arsenic  is  deposited  upon  the  copper  as  an  iron  gray 
crust. 

In  cases  of  poisoning  by  this  substance,  it  is  unsatisfac- 
tory to  apply,  in  the  first  instance,  color-giving  tests,  such 
as  the  first,  second,  and  third,  as  the  liquor  obtained  from 
the  stomach  is  itself  highly  colored  and  turbid.  It  is,  there- 
fore, desirable  to  examine  that  organ  and  its  contents  minute- 
ly, endeavoring  to  discover  any  white  granules,  or  specks, 
which  may  be  supposed  to  be  arsenious  acid,  and  if  such  are 
found,  to  examine  them  separately. 

The  contents  of  the  stomach,  the  larger  pieces  having 
been  divided,  are  to  be  boiled  in  water,  and  strained  through 
a linen  cloth.  A current  of  chlorine  gas  passed  through 
this  liquid  coagulates  and  separates  much  of  the  animal 
matter  ; or,  what  is  more  convenient,  if  the  solution  be  first 
acidulated  with  nitric  acid,  and  then  nitrate  of  silver  be 
added,  much  of  the  animal  matter  may  be  removed.  By 
the  addition  of  a solution  of  common  salt,  the  excess  of  the 
silver  salt  may  be  precipitated,  and  the  liquor  being  filtered, 
is  then  fit  for  the  third  or  fourth  of  the  foregoing  tests. 

In  the  application  of  sulphureted  hydrogen,  the  liquoi 
having  been  clarified  as  just  stated,  the  gas  is  passed  through 
it  until  it  smells  strongly.  It  is  then  to  be  boiled  for  a short 
time,  to  expel  the  excess  of  gas,  and  filtered.  The  yellow 
precipitate  of  sesquisulphuret  of  arsenic,  or  orpiment,  which 

What  is  the  process  for  detecting  it  by  arseniureted  hydrogen  ? What 
is  that  by  copper  ? In  cases  of  poisoning,  why  can  not  color  tests  be  ap- 
plied ? How  is  the  liquid  obtained  from  the  stomach  to  be  clarified  ? De- 
scribe the  test  by  sulphureted  hydrogen. 

N 2 


298 


marsh’s  test. 


Fig.  272. 


is  collected,  is  to  be  thoroughly  dried,  and  introduced,  with 
twice  its  bulk  of  black  flux,  into  the  bulb,  a,  of  a tube,  such. 

as  Fig.  272,  made  of  hard  glass.  On  the 
temperature  being  raised  by  a lamp,  metallic 
arsenic  sublimes,  forming  an  iron  black  ring 
round  the  part  b.  By  cutting  off  the  bulb  of 
the  tube  and  heating  the  black  crust  gradu- 
ally, it  slowly  sublimes  toward  the  colder  part, 
producing  a white  deposit  of  arsenious  acid  in  octahedral 
crystals. 

In  the  application  of  Marsh's  test,  the  liquor,  having  been 
cleared  either  by  chlorine  or  by  nitrate  of  silver,  as  above 
described,  is  to  be  introduced  into  a bottle  containing  dilute 
Fig.  273.  sulphuric  acid  and  zinc,  a tube,  bent  as 
represented  in  Fig.  273,  a,  passing  later- 
ally from  the  cork  ; arseniureted  hydrogen 
now  passes  off,  and  may  be  set  on  Are  as 
it  escapes  from  the  end  of  the  tube,  and  ex- 
amined by  holding  in  the  flame  a piece  of 
cold  glass,  b.  If  no  spot  be  produced,  then  the  tube,  which 
for  this  reason  should  be  made  of  a hard  glass  not  contain- 
ing lead,  is  to  be  ignited  by  a spirit  lamp  at  the  point  c, 
and  the  gas  will  deposit  its  arsenic  a little  beyond  that 
point.  In  this  manner,  the  tube  being  kept  red  hot  for 
hours,  the  smallest  quantity  of  arsenic  may  be  discovered. 

If  the  liquor,  notwithstanding  the  care  taken  to  clear  it, 
froths  when  the  hydrogen  is  disengaged,  so  as  to  interfere 
with  the  results  by  choking  the  tube,  the  gas  is  best  collect- 
ed under  a jar  at  the  pneumatic  trough,  and  may  be  subse- 
quently examined. 

The  fifth  test,  by  copper,  may  be  sometimes  advanta- 
geously applied  to  collect  the  arsenic  from  solutions  ; the 
crust  upon  the  copper  may  be  subsequently  examined,  ei- 
ther by  sublimation  or  otherwise. 

It  is  to  be  remembered  that  antimony  will  yield  results 
closely  resembling  those  of  arsenic  by  Marsh’s  test ; but  on 
heating  the  glass  plate  on  which  the  stain  has  been  depos- 
ited, if  it  be  arsenic,  it  will  totally  volatilize  away  ; but  if 
antimony,  though  the  flame  of  a blow-pipe  be  thrown  upon 

Describe  Marsh’s  test.  How  may  a small  quantity  of  metal  be  separated 
from  a large  quantity  of  liquid  by  this  test  ? When  the  liquid  froths,  what 
course  is  to  be  pursued  ? When  may  the  test  of  copper  be  advantageously 
applied  ? What  metal  closely  resembles  arsenic  in  these  respects  ? 


ARSENIC. 


299 


it,  it  will  not  disappear,  but  only  gives  rise  to  a yellow  ox- 
ide, which  turns  white  on  cooling. 

In  medico-legal  investigations,  it  should  also  be  remem- 
bered that,  as  sulphuric  acid  and  zinc  of  commerce  some- 
times contain  arsenic,  it  is  absolutely  necessary  that  the  spe- 
cimens about  to  be  used  be  critically  examined  themselves 
by  being  tried  alone  before  the  suspected  solution  is  added. 


LECTURE  LXV. 

Arsenic. — Antiseptic  Quality  of  Arsenious  Add. — An- 
tidote  for  Poisoning. — Arsenic  Acid. — Isomorphous 
with  Phosphoric  Add. — Realgar  and  Orpiment. — Ar^ 
seniureted  Hydrogen.  — Antimony. — Reduction  of. — 
Oxides,  Chlorides,  and  Sulphurets  of. — Antimoniuret- 
ed  Hydrogen. — Detection  of  Antimony. — Tellurium. 
— Uranium. — Copper.— of. — TJ&e  of  Oxide. 
— Detection  of. — Salts  of  Protoxide. 

Arsenious  Acid  possesses  a remarkable  antiseptic  qual- 
ity, and  hence  often  preserves  the.  .bodies  of  persons  who 
have  been  poisoned  by  4t  Advantage  is  also  taken  of  this 
fact  by  the  collectors  of  objects  of  natural  history  in  pre- 
serving their  specimens. 

The  antidote  for  poisoning  by  arsenic  is  the  hydrated  ses- 
quioxide  of  iron.  It  may  be  made  by  adding  carbonate  of 
soda  to  the  muriate  of  iron.  It  should  be  given  in  the 
moist  state,  mixed  with  water.  After  being  once  dried,  it 
loses  much  of  its  power.  It  produces  an  inert  basic  arsen- 
ite  of  the  peroxide  of  iron. 

Arsenic  Acid  is  found  in  nature  in  union  with  various 
bases.  It  may  be  made  by  acting  on  arsenious  acid  with 
nitric  acid,  with  the  addition  of  a little  hydrochloric  acid, 
and  evaporating  till  the  nitric  acid  is  expelled.  The  result- 
ing acid  contains  three  atoms  of  water,  and  is  isomorphous 
with  tribasic  phosphoric  acid.  The  arseniates  yield,  with 
nitrate  of  silver,  a dark-red  precipitate  of  the  tribasic  arse- 

Why  is  it  necessary  to  examine  the  sulphuric  acid  and  zinc  employed  in 
these  experiments  ? Does  arsenious  acid  possess  an  antiseptic  quality  T 
What  is  the  antidote  for  this  poison  ? How  is  it  prepared  ? How  is  arse- 
nic acid  prepared  ? What  fact  arises  from  the  isomorphism  of  arsenic  and 
phosphoric  acids  ? 


300 


ANTIMONY. 


niate  of  silver.  The  monobasic  and  bibasic  forms  of  the  acid 
are  not  known.  It  should  not  be  forgotten  in  medico-legal 
inquiries  respecting  arsenic,  that  the  arseniate  of  lime  may 
naturally  replace  phosphate  of  lime  in  bone  earth,  and  this 
acid  substitute  the  phosphoric  in  other  parts  of  the  system. 

The  protosulphuret  of  arsenic  may  be  obtained  by  melt- 
ing arsenious  acid  with  sulphur.  It  occurs  as  a mineral 
Realgar,  and  is  a red-colored  substance. 

The  sesquisulphuret  is  deposited  when  a stream  of  sul- 
phureted  hydrogen  is  passed  through  a solution  of  arsenious 
acid.  It  is  a yellow  body,  and  is  used  in  dyeing  ; it  is  also 
known  under  the  name  of  Orpiment. 

Arseniureted  Hydrogen  is  prepared  by  acting  on  an  al- 
loy of  zinc  and  arsenic  with  dilute  sulphuric  acid.  It  is  a 
colorless  gas,  burns  with  a blue  flame,  exhales  an  odor  like 
garlic.  Its  specific  gravity  is  2*695.  It  is  decomposed  by 
chlorine,  iodine,  and  the  arsenic  is  separated  by  heat  and 
by  the  rays  of  the  sun. 

ANTIMONY.  Sb  = 64*6. 

This  metal  occurs  commonly  as  a sesquisulphuret  in  na- 
ture, from  which  it  may  be  obtained  by  heating  with  iron 
filings,  a sulphuret  of  iron  forming,  and  metallic  antimony 
subsiding  to  the  bottom  of  the  crucible.  It  may  also  be 
obtained  by  fusing  the  sulphuret  with  black  flux,  which, 
produces  a sulphuret  of  potassium  and  metallic  antimony. 

Antimony  is  a blue-white  metal,  of  a very  crystalline 
structure,  and  so  brittle  that  it  may  be  pulverized.  It  melts 
at  810^  F.  Its  specific  gravity  is  6*7.  It  possesses,  at 
high  temperatures,  an  intense  affinity  for  oxygen ; a frag- 
ment of  it  the  size  of  a pea  being  ignited  on  a piece  of  char- 
coal before  the  blow-pipe,  and  then  suddenly  thrown  on  the 
table,  takes  fire,  breaking  into  a multitude  of  globules,  and 
filling  the  air  with  fumes  of  the  white  sesquioxide.  Anti- 
mony yields  the  following  compounds  : 

Sesquioxide  of  antimony Sh^O^  = 153*239. 

Antimonious  acid = 161*252. 

Antimonic  acid . Sb^O^  = 169'265. 

Sesquichloride  of  antimony  ....  Sb^Cl^  = 235*46. 

Perchloride  “ Sb^Cl^  =306*3. 

Sesquisulphuret  “ . . . . . Sb^S^  =177*5. 

Persulphuret  “ Sb^S^  =209*7. 

Oxysulphuret  - “ ....  . 2Sb^S^-\-  Sb^Os  — 5Q^’2. 

What  is  realgar  ? What  is  orpirnent  ? How  may  arseniureted  hydrogen 
be  made  ? From  what  source  is  antimony  obtained  ? What  is  the  process 
for  its  prenaration  ? What  are  its  properties  ? 


COMPOtJNDS  OP  ANTIMONY. 


301 


The  Sesquioxide  of  Antimony  may  be  made  by  adding 
to  an  acid  boiling  solution  of  chloride  of  antimony  carbon- 
ate of  soda.  It  is  a gray  powder,  and  is  the  base  of  a class 
of  salts,  among  which  tartar  emetic  may  be  mentioned. 
These  salts  give  an  orange-colored  precipitate  with  sulphur- 
eted  hydrogen. 

Antimoniom  Acid  is  produced  by  heating  the  oxide  of 
antimony,  or  antimonic  acid.  It  is  a white  powder,  and 
unites  with  bases,  forming  antimonites. 

Antimonic  Acid  may  be  prepared  by  acting  on  metallic 
antimony  with  nitric  acid. 

Sesquichlorlde  of  Antimony  is  made  by  dissolving  one 
part  of  sulphuret  of  antimony  in  five  ^ hydrochloric  acid, 
and  distilling.  As  soon  as  the  matter  which  passes  over 
becomes  solid,  the  receiver  is  to  be  changed,  and,  contin- 
uing the  heat,  the  sesquichloride  is  collected.  It  was  for- 
merly known  as  butter  of  antimony.  The  perchloride  may 
be  made  by  burning  antimony  in  chlorine  gas.  The  oxy- 
chloride is  produced  when  the  sesquichloride  is  placed  in 
contact  with  water.  It  was  formerly  known  as  powder  of 
algaroth. 

The  sesquisulphuret  occurs  abundantly  as  a mineral,  as 
has  been  said.  It  is  also  formed  by  the  action  of  sulphuret- 
ed  hydrogen  on  the  salts  of  the  oxide  of  antimony.  In  this 
case  it  is  of  an  orange  color,  in  the  former  it  has  a metallic 
aspect.  The  persuljpliuret  is  procured  when  the  sesquisul- 
phuret and  sulphur  are  boiled  in  a solution  of  potash,  the 
liquor  filtered,  and  an  acid  added,  a yellow  precipitate  going 
down.  It  was  known  formerly  as  the  Golden  Sulphuret 
of  Antimony.  The  oxysulphuret  occurs  native  as  the  red 
ore  of  antimony,  and  may  also  be  made  by  boiling  the  ses- 
quisulphuret with  a solution  of  potash.  On  cooling,  precip- 
itation of  it  takes  place.  It  is  stated,  however,  by  Berze- 
lius, that  this  is  not  a true  compound,  but  merely  a mechan- 
ical mixture  of  the  oxide  and  sulphuret  in  irregular  pro- 
portions. This  precipitate  is  also  known  under  the  name 
of  Kermes  Mineral.  From  the  liquor,  after  the  kermes  is 
separated,  an  acid  throws  down  the  golden  sulphuret  of  an- 
timony. 

What  color  is  the  precipitate  yielded  by  the  salts  of  the  sesquioxide  and 
sulphureted  hydrogen  ? How  is  antimonious  acid  prepared  ? What  is  the 
butter  of  antimony  ? What  is  the  powder  of  algaroth  ? What  is  the  aspect 
of  the  native  sesquisulphuret  ? What  is  the  golden  sulphuret  ? What  is 
kermes  mineral  ? 


S02 


imANIUM.— COPPER. 


Antimoniureted  Hydrogen. — ^When  hydrogen  is  evolved 
from  a solution  containing  tartar  emetic  (tartrate  of  anti- 
mony and  potash),  this  substance  is  produced.  It  is  a gas, 
having  a superficial  resemblance  to  arseniureted  hydrogen, 
and  when  used  as  in  Marsh’s  apparatus,  gives  a stain  on 
glass  resembling  that  of  arsenic.  From  arsenic  it  may  be 
distinguished  by  not  being  volatile. 

The  soluble  salts  of  antimony  may  be  distinguished  by 
giving  an  orange  precipitate  with  sulphureted  hydrogen,  sol- 
uble in  sulphuret  of  ammonium,  but  again  precipitated  by 
an  acid. 

Antimony  furnishes  some  valuable  alloys  : printer’s  type 
metal,  for  example,  j§  an  alloy  of  this  substance  with  lead. 
It  expands  in  the  act  of  solidifying,  and  therefore  takes  ac- 
curate impressions  of  the  interior  of  a mould. 

TELLURIUM.  Te  = 64*2.. 

Tellurium  is  a rare  metal,  of  a white  color,  very  fusible 
and  volatile,  having  several  analogies  with  selenium,  and 
uniting  with  hydrogen  to  form  tellureted  hydrogen,  which, 
with  water,  yields  a claret- colored  solution. 

URANIUM,  U=:217, 

is  likewise  a very  rare  metal,  of  the  nature  of  which  there 
are  considerable  doubts,  it  being  supposed  t^at  what  was 
formerly  regarded  as  the  metal  is  in  reality  its  protoxide. 
It  may  be  remarked,  if  these  observations  are  incorrect,  that 
uranium  has  the  highest  equivalent  of  any  of  the  element- 
ary bodies.  It  is  used  to  a small  extent  to  give  black  and 
yellow  colors  to  porcelain. 

COPPER.  Ctt=31-6. 

Copper  is  often  found  native,  and  in  certain  parts  of  the 
United  States  in  masses  of  very  great  magnitude.  It  also 
occurs  as  a carbonate  and  sulphuret.  In  the  latter  com- 
bination, it  is  found  with  the  sulphuret  of  iron,  as  yellow 
copper  ore.  This  being  roasted,  the  sulphuret  of  iron 
changes  into  oxide,  the  copper  sulphuret  remaining  un- 
changed. The  mass  is  then  heated  with  sand,  which 
yields  a silicate  of  iron,  the  sulphuret  of  copper  separating. 

How  is  antimoniureted  hydrogen  made  ? How  may  the  salts  of  antimony 
be  distinguished  ? What  are  the  properties  of  tellurium  t What  is  remark- 
able as  respects  the  alleged  atomic  weight  of  uranium  ? Under  what  forms 
does  copper  naturally  occur  ? What  is  the  process  for  its  reduction  ? 


SALTS  OP  COPPER. 


303 


This  process  is  repeated  until  all  the  iron  is  parted ; and 
now  the  sulphuret  of  copper  begins  to  change  into  the  oxide, 
which  is  finally  decomposed  by  carbon  at  a high  temperature. 

Copper  is  a red  metal,  requiring  a high  temperature  for 
fusion.  Its  specific  gravity  is  8*617.  It  has  great  tenac- 
ity, and  is  ductile  and  malleable.  A polished  plate  of  it, 
heated,  exhibits  rainbow  colors,  and  is  finally  coated  with 
the  black  oxide.  It  is  one  of  the  best  conductors  of  heat 
and  electricity.  Among  its  compounds,  the  following  may 
be  mentioned : 

Protoxide  of  copper CuO  = 39*613. 

Suboxide  “ Cu^O  = 71*213. 

Chloride  “ CuCl  =66*02. 

Dichloride  “ Cu^Cl  = 98*62, 

Disulphuret  “ Cu^S  = 79*32. 

Protoxide  of  Copper  may  be  made  either  by  igniting 
metallic  copper  in  contact  with  air,  or  by  calcining  the  ni- 
trate. It  is  a black  substance,  not  decomposable  by  heat, 
but  yielding  oxygen  with  facility  to  carbon  and  hydrogen, 
and  hence  extensively  used  in  organic  analysis.  It  is  a base, 
yielding  salts  of  a blue  or  green  color.  The  suboxide,  call- 
ed, also,  red  oxide,  occurs  native  as  ruby  copper.  It  is  a 
feeble  base.  The  disulphuret  also  occurs  native,  as  copper 
pyrites. 

Copper  is  easily  detected.  Caustic  potash  gives,  with  its 
protosalt,  a pale  blue  hydrate,  which  turns  black  on  boil- 
ing. Ammonia,  in  excess,  yields  a beautiful  purple  solu- 
tion ; ferrocyanide  of  potassium,  a chocolate-brown  precipi- 
tate ; sulphureted  hydrogen,  a black  ; and  metallic  iron,  as 
the  blade  of  a knife,  precipitates  metallic  copper. 

SALT8  OF  THE  PROTOXIDE  OF  COPPER. 

Carbonate  of  Copper. — The  neutral  carbonate  of  copper 
is  not  known  ; but  there  are  several  varieties  of  dicarbori^^ 
ates.  One,  which  passes  under  the  name  of  Mineral  Green^ 
is  formed  by  precipitating  with  an  alkaline  carbonate.  It 
occurs  naturally  in  the  form  of  Malachite.  Blue  coppei 
ore  is  ^another  dicarbonate  ; the  paint  called  Green  Verdi- 
ter  has  a similar  composition. 

Sulphate  of  Copper — Blue  Vitriol — is  prepared  for  com- 
merce by  the  oxydation  of  the  sulphuret  of  copper.  It  crys- 

What  are  its  properties  ? Which  of  its  oxides  is  used  in  organic  anal* 
ysis  ? How  may  copper  be  detected  ? Under  what  forms  do  the  carbon- 
ates of  copper  occur? 


304 


LEAD. 


tallizes  in  rhomboids  of  blue  color,  with  four  atoms  of  wa- 
ter. It  is  soluble  in  four  times  its  weight  of  cold,  and  twice 
its  weight  of  hot  water.  It  is  an  escharotic,  an  astringent, 
and  has  an  acid  reaction.  With  ammonia  it  forms  a com- 
pound of  a splendid  blue  color,  which  may  be  obtained  in 
crystals  ; with  potash,  also,  it  forms  a double  salt.  There 
are  also  subsulphates  of  copper. 

Nitrate  of  Copper,  formed  by  the  action  of  nitric  acid  on 
metallic  copper.  It  crystallizes  in  prisms  or  in  plates.  It 
acts  with  very  great  energy  on  metallic  tin.  There  is  a 
subnitrate  of  copper. 

Ars,enite  of  Copper — Scheele's  Green — produced  by  add- 
ing solution  of  arsenious  acid  to  the  solution  of  ammonia 
sulphate  of  copper. 

Copper  yields  several  valuable  alloys.  Brass  is  an  alloy 
of  copper  and  zinc  ; gun  metal,  bell  metal,  and  speculum 
metal,  of  copper  and  tin.  The  gold  and  silver  of  currency 
contain  portions  of  this  metal ; it  communicates  to  them  the 
requisite  degree  of  hardness. 


LECTURE  LXYI. 

Lead. — 'Reduction  of  Galena. — Relations  of  Lead  to 
Water. — The  Oxides  of  Lead. — Detection  of  Lead. — 
Bismuth. — Silver. — Amalgamation. — Crystallization. 
— Cupellation, — Properties  of  Silver. — Salts  of  Silver. 

LEAD.  P6“  103-6. 

Lead  occurs  under  various  mineral  forms,  but  the  most 
valuable  one  is  galena,  a sulphuret.  From  this  it  is  read- 
ily obtained.  The  galena,  by  roasting  in  a reverberatory 
furnace,  becomes  partly  converted  into  sulphate  of  lead  ; 
the  contents  of  the  furnace  are  then  mixed,  the  temperature 
raised,  and  the  sulphate  and  sulphuret  produce  sulphurous 
acid  and  metallic  lead,  the  action  being 

PbO,  So^  + PbS.  ..  = ...  2SO^  + P^2.  ' 

Lead  is  a soft  metal,  of  a bluish-white  color.  Its  speci- 

What  are  the  method  of  preparation  and  properties  of  the  sulphate  ? What 
is  Scheele’s  green  ? What  are  brass,  gun  metal,  and  bell  metal  ? Why  is 
silver  and  gold  coinage  alloyed  ? Under  what  form  does  lead  chiefly  oc- 
cur ? How  is  galena  reduced  ? 


COMPOUNDS  OF  LEAD. 


305 


fic  gravity  is  11*381.  It  melts  at  612°  F.,  and  on  the 
surface  of  the  molten  mass  an  oxide  (dross)  rapidly  forms. 
At  common  temperatures  it  soon  tarnishes.  In  the  act  of 
solidifying  it  contracts,  and  hence  is  not  fit  for  castings.  It 
possesses,  at  common  temperatures,  the  welding  property  ; 
two  bullets  will  cohere  if  fresh-cut  surfaces  upon  them  are 
brought  in  contact.  Under  the  conjoint  influence  of  air 
and  water  lead  is  corroded,  a white  crust  of  carbonate  form- 
ing. But  when  there  are  contained  in  the  water  small 
quantities  of  salts,  such  as  sulphates,  these  form  with  the 
lead  insoluble  bodies,  which,  coating  its  surface  over,  pro- 
tect it  from  farther  destruction.  For  this  reason,  lead  pipe 
can  be  used  for  distributing  water  in  cities  without  danger. 
Lead  is  one  of  the  least  tenacious  of  the  metals.  The  tar- 
trate of  lead  calcined  in  a tube  yields  one  of  the  best  pyro- 
phori.  On  bringing  it  into  the  air  at  common  temperatures, 
it  spontaneously  ignites. 

Of  the  compounds  of  lead,  the  following  are  some  of  the 
more  important : 


Protoxide  of  lead 
Sesquioxide  “ 

Peroxide  “ 

Red  oxide  “ 

Chloride  “ 

Iodide  “ 

Sulphuret  “ 


PhO  =111-613. 
P62O3  = 231-239. 
P6O2  =119-626. 
P63  04  = 342-852. 
PbCl  = 139-62. 
Phi  = 229-9. 
PbS  =119-7. 


The  protoxide  is  made  by  heating  lead  in  the  air  ; it  is 
a yellow  body,  which  fuses  at  a bright  red  heat.  In  the 
first  state  it  is  called  massicot ; in  the  latter,  litharge.  It 
yields  a class  of  salts,  being  a base.  It  is  slightly  soluble 
in  water.  The  peroxide  is  made  from  red  lead  by  digest- 
ing it  with  nitric  acid,  which  dissolves  out  the  protoxide, 
and  leaves  the  substance  as  a puce  colored  powder.  The 
red  oxide,  or  red  lead,  is  rnade  by  calcining  lead  in  a cur- 
rent of  air  at  600°  or  700°  F.  It  is  used  in  the  manufac- 
ture of  flint  glass.  The  chloride  is  made  by  the  action  of 
hot  hydrochloric  acid  on  protoxide  of  lead  : on  cooling,  it  is 
deposited  in  crystals.  The  iodide  is  formed  when  any  solu- 
ble iodide  is  added  to  protosalt  of  lead ; it  is  a beautiful 
yellow  precipitate,  soluble  in  boiling  water,  forming  a color- 
less solution,  which,  on  cooling,  deposits  golden  crystals. 


Why  can  not  lead  be  used  for  castings  ? What  is  the  action  of  pure  wa- 
ter, and  water  containing  salts,  upon  it  ? What  is  massicot  ? How  is  it 
prepared  ? What  is  litharge  ? How  is  the  peroxide  prepared  ? How  is 
minium  made  ? 


306 


SALTS  OF  LEAD.— BISMUTH. 


The  sulphuret  is  galena  ; it  crystallizes  in  cubes,  and  has  a 
high  metallic  lustre. 

Lead  is  easily  detected  by  sulphureted  hydrogen,  which 
throws  it  from  its  solutions  as  a deep  brown  or  black  pre- 
cipitate, and  by  the  iodide  of  potassium  or  chromate  of  pot- 
ash, which  gives  with  it  a yellow  precipitate.  Sulphuric 
acid  yields  with  its  salts  a white  insoluble  sulphate  of  lead. 

SALTS  OF  THE  PROTOXIDE  OF  LEAD. 

Carbonate  of  Lead — White  Lead — Ceruse. — This  salt 
forms  as  a white  precipitate  when  an  alkaline  carbonate  is 
added  to  a solution  of  a salt  of  lead.  Large  quantities  of 
it  are  consumed  in  the  arts  as  white  paint.  For  commerce 
it  is  procured  by  mixing  litharge  with  water  containing  a 
small  proportion  of  acetate  of  lead  \ carbonic  acid  gas  is  then 
sent  over  it,  and  the  carbonate  rapidly  forms.  It  is  also 
made  by  exposing  metallic  lead  in  plates  to  the  action  of 
the  vapor  of  vinegar,  air,  and  moisture,  the  metal  becom- 
ing oxydized  and  carbonated. 

Nitrate  of  Lead  may  be  formed  by  dissolving  litharge 
in  dilute  nitric  acid ; it  crystallizes  in  opaque  white  octa- 
hedrons, which  dissolve  in  seven  or  eight  times  their  weight 
of  cold  water.  They  contain  no  water  of  crystallization, 
and  are  decomposed  at  a red  heat,  as  stated  in  the  descrip- 
tion of  nitrous  acid.  By  the  action  of  ammonia,  three  oth- 
er nitrates  of  lead  may  be  obtained.  ^ 

Among  the  alloys  of  lead  are  the  soft  solders.  Two  parts 
of  lead  and  one  of  tin  constitute  plumber’s  solder ; one  of 
lead  and  two  of  tin,  fine  solder. 

BISMUTH.  J5i  = 71*07. 

Bismuth  is  found  both  native  and  as  a sulphuret.  It  is 
of  a reddish  color,  melts  at  497°,  and  may  be  obtained  in 
beautiful  cubic  crystals  by  cooling  a quantity  of  it  until 
solidification  commences,  then  breaking  the  surface  crust 
and  pouring  out  the  fluid  portion. 

When  bismuth  is  dissolved  in  nitric  acid,  and  the  solution 
poured  into  water,  the  white  subnitrate  is  deposited,  once 
used  as  a cosmetic  ; when  this  is  washed,  and  subsequently 
heated,  the  protoxide  is  left.  There  is  also  a peroxide. 

How  may  lead  be  detected  ? Mention  some  of  the  methods  by  which 
white  lead  may  be  made.  What  change  does  the  nitrate  undergo  at  a red; 
heat?  Of  what  are  the  common  solders  composed?  What  are  the  propsq 
erties  of  bismuth  ? " 


SILVER. CRYSTALLIZATIOTf. CUPELLATION.  307 


Fusible  metal  is  an  alloy  of  eight  parts  of  bismuth,  five 
of  lead,  and  three  of  tin ; it  melts  below  the  boiling  point 
of  water,  and  may  be  obtained  in  crystals. 

SILVER.  A^  = 108-31. 

Silver  is  found  native,  and  as  a sulphuret  and  a chlo* 
ride,  occurring,  also,  with  a variety  of  other  metals,  and  in 
small  proportion  with  galena.  When  disseminated  as  a 
metal  through  ores,  it  may  be  collected  from  them  by  amal- 
gamation with  quicksilver,  and,  on  distilling,  the  quicksil- 
ver is  driven  off. 

When  it  is  obtained  from  the  sulphuret,  that  ore  is  roast- 
ed with  common  salt,  which  changes  it  into  a chloride. 
This,  with  the  impurities  with  which  it  may  be  associated, 
is  put  into  barrels,  which  revolve  on  an  axis,  along  with 
water,  pieces  of  iron,  and  metallic  mercury ; the  iron  re- 
duces the  chloride  to  the  metallic  state,  and  the  silver 
amalgamates  with  the  mercury.  This  is  washed  from  the 
impurities,  strained  through  a bag  to  separate  the  excess  of 
mercury,  and  the  residue  is  driven  ofi^  by  distillation.  . 

The  extraction  of  silver,  when  it  occurs  in  small  quantity 
with  lead,  has  been  recently  much  improved  by  the  intro- 
duction of  the  process  of  crystallization.  It  depends  upon 
the  fact  that  an  alloy  of  lead  and  silver  is  more  fusible  than 
lead.  A large  quantity  of  argentiferous  lead  is  melted  and 
allowed  to  cool.  As  the  setting  goes  on,  the  first  portions 
which  solidify  are  pure  lead  ; they  may  be  removed  by  iron 
colanders,  and  by  continuing  the  process  there  is  finally  left 
a portion  containing  all  the  silver.  This  is  exposed  to  a 
red  heat,  and  a stream  of  air  directed  over  it ; oxydation  of 
the  lead  takes  place,  and  the  litharge  is  removed  by  the 
blast,  the  process  being  finally  completed  by  cupellation. 

A cupel  is  a shallow  dish  made  of  bone  ashes,  and  is  very 
porous.  In  this,  if  an  alloy  of  lead  and  silver  be  heated 
with  access  of  air,  the  lead  oxydizes,  and,  melting  into  a 
glass,  soaks  into  the  cupel,  or  may  be  driven  from  the  sur- 
face by  a blast  of  air  directed  from  a bellows.  At  the  same 
time,  any  copper  or  other  base,  metal  oxydizes  and  is  re- 
moved along  with  the  lead.  The  completion  of  the  process 
is  indicated  by  the  silver  assuming  a certain  brilliancy,  or 
flashing,  as  the  workmen  term  it. 

"What  is  fusible  metal  ? Under  what  forms  does  silver  commonly  occur? 
How  is  it  reduced  from  the  sulphuret  ? What  is  the  process  of  amalgama- 
tion ? What  is  the  process  of  crystallization  ? What  of  cupellation  f 


308 


COMPOUNDS  OF  SILVER. 


Silver  is  a white  metal  capable  of  receiving  a brilliant 
polish.  It  is  malleable  and  ductile,  an  excellent  conductor 
of  heat  and  electricity.  Its  specific  gravity  is  10'5.  It 
melts  at  1873°  F.,  and,  when  melted,  absorbs  a large  quan- 
tity of  oxygen,  giving  it  out  again  as  soon  as  it  solidifies, 
and  assuming  a frosted  or  porous  appearance.  The  pres- 
ence of  a minute  quantity  of  copper  prevents  this  efiect. 
Silver  is  so  soft  that,  for  making  plate  or  coins,  it  requires 
to  be  alloyed  with  a portion  of  copper  ; from  this  it  may  be 
purified  by  dissolving  it  in  nitric  acid,  and  precipitating  the 
silver  as  chloride  by  a solution  of  common  salt.  Silver 
shows  little  disposition  to  unite  with  oxygen,  though  it  tar- 
nishes readily  % the  action  of  sulphureted  hydrogen.  It 
yields  three  oxides,  but  of  its  compounds  the  following  are 
the  most  important : 

Protoxide  of  silver  ....  AgO  = 116*323. 

Chloride  ...  , AgCl  = U3'78. 

Iodide  “ ....  Agl  =234-48. 

Sulphuret  “ ....  AgS  = 124*43. 

The  protoxide  may  be  made  by  t^ie  action  of  caustic  pot- 
2|jSh  on  a solution  of  nitrate  of  silver,  or  by  boiling  recently- 
prepared  chloride  in  potash.  It  is  a dark  powder,  which 
may  be  reduced  by  heat  alone.  The  chloride  is  sometimes 
found  native,  as  horn-silver,  and  may  be  made  by  precipita- 
tion from  the  nitrate  by  hydrochloric  acid,  or  a soluble  chlo- 
ride. Like  the  iodide,  it  turns  dark  on  exposure  to  the  in- 
digo rays,  and  hence  is  used  in  photogenic  drawing.  The 
sulphuret  is  produced  whenever  sulphureted  hydrogen  acts 
on  oxide  of  silver,  or  even  metallic  silver ; it  is  a black  com- 
pound. 

Silver  is  easily  detected  by  precipitation  as  a chloride  : a 
curdy,  white  precipitate,  insoluble  in  water,  but  soluble  in 
ammonia.  It  turns  dark  on  exposure  to  the  sun. 

SALTS  OF  THE  PROTOXIDE  OF  SILVER. 

Nitrate  of  Silver — Lunar  Caustic — procured  by  dis- 
solving silver  in  nitric  acid,  diluted  with  twice  its  weight 
of  water.  It  crystallizes  in  tables  which  are  not  deliques- 
cent and  contain  no  water  of  crystallization.  It  enters  into 
fusion  at  426°  F.,  but  at  higher  temperatures  undergoes  de- 

What  are  the  properties  of  silver?  Why  does  it  frequently  require  to 
be  alloyed  with  copper  ? What  remarkable  relation  does  it  possess  to  ox- 
ygen ? How  may  the  protoxide  be  prepared  ? What  changes  do  the  chlo- 
ride and  iodide  exhibit  under  the  influence  of  light  ? How  may  silver  be 
detected  ? How  is  lunar  caustic  made  ? 


MERCURY. 


309 


composition.  It  is  frequently  cast  into  small  sticks  and  used 
by  surgeons  as  a cautery.  It  is  soluble  in  its  own  weight 
of  cold  and  half  its  weight  of  hot  water,  and,  when  in  con- 
tact with  organic  matter,  turns  black  in  the  rays  of  the  sun. 

Ammoniuret  of  Silver — Bertlwllet' s Fulminating  Sil- 
ver— is  formed  by  digesting  precipitated  oxide  of  silver  in 
ammonia.  It  explodes  with  the  utmost  violence  under  the 
feeblest  friction,  with  the  evolution  of  nitrogen  and  the  va- 
por of  water. 


LECTURE  LXYII. 

Mercury. — Process  o f Reduction. — The  Liquid  State  of 
— Its  Oxides. — Calomel  and  Corrosive  Suhlimole. — 
Detection  of  Mercury. — Its  Salts. — Amalgams. — Gold. 
— Chloride  of.  — Purple  of  Cassius.  — Palladium. — 
Platinum. — Its  Catalytic  Effects. — Platinum  Black. 
— Iridium. — Rhodium. 


MERCURY.  Hg  — 202. 

Mercury  may  be  obtained  from  the  bisulphuret  (cinna- 
bar) by  distillation  with  iron  filings.  It  is  also,  to  a certain 
extent,  found  native. 

The  striking  characteristic  of  mercury  is  its  liquid  condi- 
tion. Its  melting  point  is  the  lowest  of  that  of  any  of  the 
metals,  being  — 39°  F.  Its  specific  gravity  at  47°  F.  is 
13-545.  It  boils  at  662°  F.  Kept  at  that  temperature  in 
the  air  for  a length  of  time,  it  produces  red  oxide,  but  at 
common  temperatures  it  is  not  acted  on  by  the  air.  It  may 
be  freed  from  impurities  for  the  purposes  of  the  laboratory 
by  being  kept  in  contact  with  dilute  nitric  acid.  It  gives 
the  following  compounds  of  interest : 


Protoxide  of  mercury 
Peroxide  “ 
Protochloride  “ 
Bichloride  “ 
Protosulphuret  “ 
Bisulphuret  “ 


. HgO  — 210  013. 
. HgO.,  =218-020. 
. HgCl  =237-42. 

. HgCl^  = 272-84. 

. HgS  =218-1. 

. HgS^  = 234-2. 


The  protoxide  may  be  made  by  triturating  calomel  with 
potash  water  in  a mortar.  It  is  a black  powder,  which  is 


Under  what  forms  does  mercury  commonly  occur  ? What  is  the  most 
striking  property  of  this  metal  ? How  may  it  be  purified  ? What  are  the 
properties  of  the  protoxide  of  mercury  ? 


COMPOUNDS  OP  MERCURY 


•sio 

decomposed  by  light  or  any  of  the  reducing  agents.  The 
peroxide  may  be  formed,  as  stated  above,  by  the  action  of 
air  on  hot  mercury,  but  more  easily  by  dissolving  mercury 
in  nitric  acid,  and  evaporating  and  heating  the  salt  until  no 
more  fumes  of  nitrous  acid  are  evolved.  It  is  a red  pow- 
der, and  when  warmed  becomes  almost  black,  the  color  re- 
turning as  the  temperature  descends.  Like  the  former,  it  is 
a base,  and  yields  a class  of  salts. 

The  Protochloride,  or  Calomel,  may  be  made  by  adding 
hydrochloric  acid  to  the  protonitrate  of  mercury,  or  by  sub- 
liming a mixture  of  bichloride  of  mercury  and  mercury.  It 
is  a white  powder,  insoluble  in  water,  and  darkens  slowly 
by  exposure  to  sunshine.  The  bichloride  (or  Corrosive  Sub- 
limate) is  formed  when  mercury  burns  in  chlorine  gas,  but 
more  economically  by  sublimation  from  a mixture  of  per- 
sulphate of  mercury  and  common  salt.  It  is  a heavy,  white 
crystalline  body,  soluble  in  water,  has  a metallic  taste,  and 
is  poisonous.  The  antidote  for  it  is  albumen  (the  white  of 
an  egg). 

Of  the  sulphurets  of  mercury,  the  protosulphuret  is  black, 
and  the  bisulphuret  commonly  red  ; in  this  case  it  passes 
in  commerce  under  the  name  of  vermilion,  and  is  used  as  a 
paint.  It  can  be  obtained,  however,  quite  black,  a pecu- 
liarity already  observed  in  the  case  of  the  peroxide,  and  still 
more  strikingly  in  the  biniodide,  which  may  be  sublimed 
in  beautiful  yellow  crystals,  which  become  of  a splendid 
scarlet  color  by  merely  being  touched. 

Mercury  may  be  detected  by  being  precipitated  from  its 
soluble  combinations  by  metallic  copper  as  a metal.  Its 
salts,  either  alone  or  with  carbonate  of  soda,  heated  in  a 
tube,  yield  metallic  mercury,  which  volatilizes. 

SALTS  OF  THE  OXIDES  OF  MERCURY. 

Nitrates  of  the  Oxides  of  Mercury. — When  cold  dilute 
nitric  acid  acts  on  mercury,  it  gives  rise  to  neutral  or  basic 
protosalts,  as  the  acid  or  mercury  is  in  excess  ; if  the  acid 
be  hot,  a pernitrate  forms  ; these  salts  are  decomposed  by 
an  excess  of  water,  giving  rise  to  basic  compounds.  The 
neutral  pernitrate  exists  in  solution  only. 

What  are  the  properties  of  the  peroxide  of  mercury  ? What  is  calomel  ? 
What  is  corrosive  sublimate  ? What  is  the  antidote  to  it  ? For  what  purpose 
is  the  bisulphuret  employed  ? What  change  occurs  to  the  yellow  biniodide 
when  4t  is  touched  ? How  may  mercury  be  detected  ? How  are  the  proto- 
nitrate  and  the  persulphate  prepared  ? 


GOLD. 


311 


Persulphate  of  Mercury  is  formed  by  boiling  sulphuric 
acid  and  mercury,  and  evaporating  to  dryness.  It  occurs  in 
the  form  of  a white  granular  mass,  and  is  decomposed  by 
water,  giving  a yellow  precipitate,  a subsulphate  called 
Turpeth  Mineral. 

The  alloys  of  mercury  are  called  amalgams  ; the  amal- 
gam of  tin  is  used  for  silvering  looking-glasses,  and  that  of 
zinc  for  exciting  electrical  machines. 

GOLD.  199-2. 

Gold  is  found  native,  and  may  be  obtained  by  washing 
or  by  amalgamation  with  mercury.  It  may  be  purified 
from  silver  by  quartation  ; that  is,  fusing  it  with  three 
times  its  weight  of  silver,  and  then  acting  on  the  mass  with 
nitric  acid.  The  gold  is  left  as  a dark  powder. 

From  all  other  metals  gold  is  distinguished  by  its  yellow 
color.  Its  specific  gravity  is  19*3.  It  melts  at  2016°  F. 
It  is  the  most  malleable  of  all  the  metals,  as  is  proved  by 
gold-leaf,  which  may  be  obtained  jo"^oo  thick- 

ness ; is  not  acted  upon  by  the  air  or  oxygen.  Objects  of 
art  covered  with  it  have  retained  their  brilliancy  for  thou- 
sands of  years.  No  acid  alone  dissolves  it ; but  it  is  solu- 
ble in  aqua  regia,  and  also  by  chlorine. 

It  can,  however,  be  made  to  yield  two  oxides,  a protox- 
ide and  a teroxide  ; and  two  chlorides  having  the  same 
constitution  ; the  terchloride  is  formed  by  the  action  of  ni- 
tro-muriatic  acid  (aqua  regia)  on  gold.  When  evaporated, 
it  yields  red,  deliquescent  crystals.  Deoxydizing  agents, 
such  as  protosulphate  of  iron,  reduce  it  to  the  metallic  state  ; 
this  is  probably  due  to  their  decomposing  water  and  present- 
ing hydrogen  to  the  chloride.  Hydrogen  gas  decomposes 
the  terchloride,  and,  by  heating  it,  it  first  changes  into  the 
protochloride  and  then  into  metallic  gold.  With  a solution 
of  tin  it  forms  the  Purple  of  Cassius.  This  and  the  ac- 
tion of  protosulphate  of  iron  serve  as  a test  for  it. 

PALLADIUM.  Pd  = 53-3. 

Palladium  is  found  associated  with  platinum,  and  is  best 
obtained  from  the  cyanide  of  palladium  by  ignition.  It  is 
a white  metal,  requiring  a high  temperature  for  fusion ; 

Under  what  forms  does  gold  occur  ? What  is  quartation  ? What  are  the 
properties  of  this  metal  ? How  many  oxides  does  it  yield  ? How  is  the 
terchloride  prepared  ? What  is  the  purple  of  Cassius  ? With  what  metal 
is  palladium  generally  associated  ? What  are  its  properties  ? 


312 


PLATINUM. 


specific  gravity  11*5.  It  does  not  tarnish  in  the  air,  is  dis- 
solved by  nitric  acid  and  aqua  regia,  is  one  of  the  wielding 
metals,  and,  when  heated,  acquires  a purple  oxydation  like 
watch  spring.  It  is  used  to  some  extent  by  dentists.  Its 
compounds  are  not  of  importance. 

PLATINUM.  = 98-84. 

Platinum  is  found  native,  but  always  associated  with 
other  metals.  It  is  obtained  by  first  forming  a chloride  of 
platinum  and  ammonium  ; this,  when  ignited,  leaves  pure 
spongy  platinum,  which  being  exposed  to  powerful  pressure, 
and  then  alternately  made  white  hot  and  hammered,  be- 
comes a solid  mass. 

Platinum  is  a white  metal.  Its  specific  gravity  is  very 
high,  being  21*5.  It  can  not  be  melted  in  a furnace,  but 
fuses  before  the  oxyhydrogen  blow-pipe.  It  is  a welding 
metal,  and  on  this  fact  its  preparation  depends.  ' It  is  very 
malleable  and  ductile,  is  not  acted  upon  by  oxygen,  air,  or 
any  acid  alone,  but  dissolves  in  aqua  regia.  It  possesses  the 
extraordinary  property  of  causing  hydrogen  and  oxygen  to 
unite  at  common  temperatures,  an  elfect  which  takes  place 
with  remarkable  energy  when  the  metal  is  in  a spongy  state. 
A jet  of  hydrogen  falling  upon  spongy  platina  in  the  air 
makes  it  red  hot,  and  presently  after  the  gas  takes  fire.  It 
also  brings  about  the  rapid  transformation  of  alcohol  into 
acetic  acid,  and  various  other  chemical  changes. 

Fi^.  274.  If  a quantity  of  ether  be  poured  into 

a glass  jar.  Fig.  274,  and  a coil  of  pla- 
tinum wire,  recently  ignited,  be  intro- 
duced, the  metal  continues  to  glow  so 
long  as  any  ether  is  present. 

Platinum  is  invaluable  to  the  chem- 
ist. It  furnishes  a variety  of  imple- 
ments of  great  value,  and  is  met  with 
under  the  forms  of  crucibles,  tubes,  wire, 
foil,  &c. 

Platinum  Black  is  prepared  by  slow- 
ly heating  to  212°  a solution  of  chloride 
of  platinum,  to  which  an  excess  of  carbonate  of  soda  and 

What  superficial  effect  takes  place  when  it  is  heated  in  the  air  ? How 
is  platinum  obtained  Trom  its  ores  ? What  is  the  specific  gravity  of  this 
metal  ? By  what  acid  may  it  be  dissolved  ? What  remarkable  relations 
does  it  possess  to  hydrogen  gas  ? Under  its  influence,  what  is  alcohol 
transmuted  into  ? What  is  platinum  black  ? 


IRIDIUM. RHODIUM. 


313 


some  sugar  have  been  added.  It  is  a dark  powder,  and 
possesses  the  property  of  determining  a variety  of  chemical 
changes  with  much  more  energy  than  platinum  in  mass. 

Platinum  can  be  caused  to  yield  two  oxides,  which  are 
not  of  any  importance  ; and  two  analogous  chlorides,  of 
which  the  bichloride,  which  is  the  common  platinum  salt, 
is  made  by  dissolving  the  metal  in  nitro-muriatic  acid,  and 
evaporating  to  a sirup.  It  is  soluble  in  water  and  alcohol, 
and  is  used  for  detecting  the  salts  of  potash. 

IRIDIUM.  Jr  = 98-84. 

Iridium  is  associated  with  platinum.  It  is  said  to  have 
been  found  of  specific  gravity  26*00.  Dr.  Hare  has  obtain- 
ed it  21*8;  it  is,  therefore,  the  heaviest  of  the  metals.  Its 
name  is  derived  from  the  different  colors  (iris)  of  its  com- 
pounds. 

RHODIUM.  R = 52-2. 

Like  the  former  metal,  rhodium  is  associated  with  the 
platina  ores.  It  is  a hard  white  metal ; its  specific  grav- 
ity is  11*00,  and  is  sometimes  used  to  form  tips  to  metallic 
pens. 

Wliat  are  the  properties  of  iridium  ? What  are  those  of  rhodium  ? 

0 


PART  IV. 

ORGANIC  CHEMISTRY. 


LECTURE  LXYIIL 

Peculiarities  of  Organic  Bodies. — Their  constituent  El- 
ements.— Prone  to  Decomposition.  — Carbon  always 
present. — Compound  Radicals. — Doctrine  of  Substi- 
tution.— Types. — Action  of  Heat. — Eremacausis. — 
Propagation  of  Decay. — Action  of  Acids  and  Alkalies. 

The  theory  of  molecular  arrangement,  which  has  been  al- 
ready given,  forms  the  foundation  of  organic  chemistry.  It 
asserts  that  the  characters  of  compound  bodies  do  not  alone 
depend  on  the  nature  of  their  constituent  elements,  nor  even 
on  the  relative  amount  of  those  elements ; but  that  varia- 
tion of  physical  forms  may  result  from  atoms  of  the  same 
name  and  of  the  same  number  arranging  themselves  in  sub- 
ordinate groups,  which  groups  then  unite  with  each  other. 

The  leading  ultimate  elements  of  organized  bodies  are 
carbon,  hydrogen,  nitrogen,  and  oxygen.  Almost  all  organic 
bodies  arise  from  variations  in  the  number  and  grouping  of 
identical  elements. 

Now  a partial  consideration  of  the  conditions  under  which 
the  theory  of  molecular  arrangement  acts,  exhibits  to  us  a 
most  striking  difference  in  the  nature  of  the  compounds 
formed  upon  its  principles  and  the  compounds  heretofore  de- 
scribed as  examples  of  inorganic  chemistry.  In  the  one, 
peculiarity  of  grouping  is  the  grand  feature  ; in  the  other, 
the  character  of  the  combining  elements.  Urea  differs  from 
the  cyanate  of  ammonia  in  the  arrangement  of  its  constitu- 
ents only  ; but  the  leading  mark  of  distinction  between  sul- 
phuric and  phosphoric  acids  is,  that  the  one  contains  sul- 
phur and  the  other  phosphorus. 

The  number  of  substances  which,  besides  the  four  men- 


On  what  do  the  characters  of  compound  bodies  depend  ? Of  what  four 
reading  elementary  bodies  are  organic  substances  chiefly  composed  ? In 
what  striking  respect  do  the.se  substances  differ  from  inorganic  ones  ? 


CHARACTERS  OF  ORGANIC  BODIES. 


315 


tioned  above,  enter  into  the  composition  of  organic  bodies  is 
very  limited.  Among  such  may  be  mentioned  potash,  soda, 
lime,  magnesia,  oxide  of  iron,  chlorine,  fluorine,  sulphur,  phos-- 
phorus,  and  silica.  Some  of  those  bodies,  such  as  alumina, 
which  appear  to  take  the  lead  in  inorganic  productions,  arc 
here  scarcely  seen. 

While  the  laws  of  inorganic  chemistry  appear  to  be  fully 
in  operation  as  respects  the  bodies  on  the  study  of  which 
we  are  now  entering,  there  are  some  peculiarities  which 
deserve  to  be  pointed  out.  The  remarkable  instability,  or 
proneness  to  decomposition,  which  so  many  of  them  exhibit, 
generally  tends  to  the  production  of  secondary  compounds  of 
a much  more  stable  nature.  At  a red  heat  all  organized 
bodies  are  decomposed  ; and  as  the  elements  of  which  thej 
consist  are  endowed  with  the  most  energetic  affinities,  any 
extensive  elevation  of  temperature  tends  to  impress  upon 
them  a change.  ‘With  but  few  exceptions,  the  attempts 
which  have  hitherto  been  made  to  produce  them  artificial* 
ly  have  been  abortive  ; but  this  is,  probably,  rather  due  tc 
our  want  of  knowledge  than  any  intrinsic  impossibility  in 
efi’ecting  such  combinations. 

With  the  exception  of  a few  bodies,  such  as  ammonia, 
which,  in  point  of  fact,  belong  rather  to  inorganic  chemistry, 
all  organized  bodies  contain  carbon.  Of  late,  by  indirect 
processes,  chemists  have  succeeded  in  obtaining  pseudo-or- 
ganized compounds,  into  the  constitution  of  which  such  bod- 
ies as  platinum  and  arsenic  enter. 

In  inorganic  chemistry  we  see  a constant  disposition  to 
the  binary  form  of  union  : a disposition  wffiich  is  well  rep- 
resented by  the  electro-chemical  theory.  Thus,  potassium 
unites  with  oxygen,  two  bodies  together,  to  form  potash  ; 
and  this,  again,  with  sulphuric  acid,  two  bodies  together,  to 
form  sulphate  of  potash.  In  very  many  instances,  the  same 
thing  can  be  traced  in  organic  chemistry;  only  here,  instead 
of  having  such  bodies  as  chlorine  or  iodine,  potassium  or  so- 
dium to  deal  with,  we  find  compound  bodies  which  dis- 
charge analogous  functions.  These  bodies  go  under  the 
name  of  compound  radicals.  They  may  be  divided  into  dis- 
tinct groups,  some  discharging  the  duty  of  electro-negative, 

What  other  elements  are  found  among  organic  bodies  ? In  their  decom- 
position, what  do  they  generally  produce  ? Can  any  of  them  withstand  a 
red  heat  ? Can  they  be  formed  oy  artificial  means  ? What  is  meant  by 
compound  ridicals? 


1 


310  COMPOUND  RADICALS. 

some  of  electro-positive,  and  some  of  indifferent  bodies, 
several  cases  they  have  been  insulated,  but  in  others  t 
remain  as  yet  as  ideal  or  hypothetical  bodies. 


Table  of  Compound  Radicals. 


Amidogen. 

Iridiocyanogen. 

Acetyle. 

Oxalyle. 

Sulphocyanogen. 

Kakodyle. 

Cyanogen. 

Mellone. 

M ethyle. 

Ferrocyanogen. 

Uryle. 

Formyle, 

Ferridcyanogen. 

Benzyle. 

Cetyle. 

Cobaltocyanogen. 

Salicyle. 

Amyle. 

Chromocyanogen. 

Platinocyanogen. 

Cinnamyle. 

Ethyle. 

Glyceryle. 

The  qualities  of  bodies  depending  as  much  on  the  mode 
of  arrangement  of  their  constituent  particles  as  on  the  chem-  ; 

ical  nature  of  those  particles,  it  has  been  found  convenient 
to  arrange  them  in  groups,  according  to  their  type  of  struc- 
ture ; thus,  for  instance,  in  the  former  department  of  chem-  i 

istry,  such  bodies  as  hydrochloric,  hydriodic,  hydro  bromic  j 

acids  may  be  arranged  together  as  belonging  to  one  type  ; 
and  from  the  first  of  these  all  the  rest  may  be  conceived  as 
arising,  by  substituting  an  atom  of  iodine,  bromine,  fluorine, 

&o;,  for  the  atom  of  chlorine  which  it  contains.  I 

The  bodies  which  can  thus  be  substituted  for  each  other  j 

appear  to  have  certain  relationships  ; for  the  substitution  of  i| 

a given  substance  can  not  take  place  indiscriminately  by  all 
other  bodies.  As  a general  rule,  in  inorganic  combinations,  j 

electro-negative  bodies  can  only  be  substituted  by  electro-  i 

negative,  and  electro-positive  by  electro-positive.  But  many  j 

of  the  most  prominent  cases  in  organic  chemistry  are  pre-  j 

cisely  the  reverse.  In  them,  for  example,  we  find  chlorine,  j 

a powerful  electro-negative,  taking  the  place  of  hydrogen, 
an  equally  powerful  electro-positive  body,  and,  in  the  com- 
pound, discharging  all  its  functions.  For  these  reasons,  it 
has  been  supposed  that  the  electro-chemical  theory  fails  to 
furnish  any  explanation  ; but  I have  proved  that  chlorine,  f 

like  many  other  bodies,  can  assume  different  allotropic  j 

states  ; at  one  time  being  an  active  electro-negative  body,  j 

and  at  another  quite  passive.  Moreover,  it  ought  not  to  be  1 

forgotten  that  hydrogen,  in  relation  to  carbon,  is  as  much  an  | 

electro-negative  body  as  chlorine  itself. 

A chemical  type  is,  therefore,  a system,  or  group  of  atoms 

"Wliat  compound  radicals  are  known?  Under  what  circumstances  can 
bodies  be  substituted  for  each  other?  Is  there  any  difference  in  this  re- 
spect betw^een  inorganic  and  organic  bodies  ? "WTiat  is  a chemical  type  ? 


DESTRUCTION  OF  ORGANIC  COMPOUNDS.  .'U? 

of  a certain  number,  arranged  in  a certain  relationship  with 
each  other.  From  this  each  atom  may  be  displaced,  and 
one  of  another  kind  substituted  in  its  stead  ; and  this  may 
be  carried  forward  until  not  one  of  the  original  atoms  is 
left,  the  new  group  officiating  in  all  respects  like  its  ])rcde- 
cessor.  But  should  one  of  the  atoms  be  displaced,  and  no 
new  one  substituted  for  it,  then,  the  remaining  atoms  chang- 
ing their  position,  the  type  is  broken  up  and  a new  one  is 
the  result. 

Organic  compounds,  being  for  the  most  part  composed 
of  carbon,  hydrogen,  nitrogen,  and  oxygen,  exhibit  a con- 
stant tendency  to  break  up  into  subordinate  groups,  and 
eventually  to  give  rise  to  the  production  of  the  simpler  bi- 
nary bodies,  carbonic  acid,  water,  and  ammonia.  The  car- 
bon constantly  inclines  to  unite  with  oxygen  to  form  carbonic 
acid,  the  hydrogen,  in  the  same  manner,  to  form  water,  or, 
with  the  nitrogen,  to  produce  ammonia  ; and  these  tenden- 
cies may  be  satisfied  in  a variety  of  ways.  Elevations  of 
temperature  in  the  open  air  at  once  give  rise  to  carbonic 
acid,  water,  and  free  nitrogen  ; or  if  in  close  vessels  out  of 
the  contact  of  air,  to  an  extensive  series  of  compounds,  dif- 
fering in  each  case  with  the  substance  exposed,  and  of  a 
less  complex  constitution.  Even  in  the  air,  at  common 
temperatures,  a slow  action  often  goes  on,  as  in  the  decay 
of  wood  or  the  souring  of  wine ; hence  called  eremacausis 
(slow  combustiow). 

When  a combustible  substance  is  ignited  in  the  air  at 
one  point,  the  burning  presently  spreads  throughout  the 
whole  mass  ; and»in  the  slow  combustion,  eremacausis,  the 
same  takes  place.  A substance  undergoing  such  a change, 
if  placed  in  contact  with  another  capable  of  undergoing  it, 
propagates  its  effect  throughout  the  whole  mass.  For  this 
reason,  the  decay  of  yeast,  a ferment,  impresses  a metamor- 
phosis on  sugar,  compelling  it  to  give  off  carbonic  acid  gas  ; 
and  putrefaction  of  fresh  meat  is  easily  brought  on  by  the 
contact  of  putrid  animal  matter. 

Nitric,  sulphuric,  and  other  strong  acids  impress  striking 
changes  when  heated  with  organic  matters;  thus,  when  the 
former  acts  on  starch,  oxalic  acid  is  formed  ; when  sulphuric 

Under  what  circumstances  do  new  types  result?  What  are  the  binary 
bodies  eventually  produced  ? What  is  the  result  of  elevation  of  tempera- 
ture in  the  open  air?  What  in  close  vessels?  What  is  meant  by  erema- 
causis? In  what  respect  does  eremacausis  resemble  common  combustion? 
What  is  the  effect  of  strong  acids  and  alkalies  on  organic  bodies  ? 


318 


THE  NON-NITROGENIZED  BODIES. 


acid  acts  on  oxalic,  it  totally  destroys  it,  resolving  it  into 
carbonic  acid,  carbonic  oxide,  and  water.  In  the  same  man- 
ner, also,  basic  bodies  produce  striking  changes,  generally 
giving  rise  to  the  production  of  acids,  and  the  evolution  of 
hydrogen  and  ammonia. 

In  the  present  state  of  organic  chemistry,  it  is  impossible 
to  present  a perfect  system  of  arrangement,  as  in  inorganic 
chemistry,  or  one  approaching  to  the  finish  of  that  depart- 
ment. The  course,  therefore,  which  I shall  now  take  is  rec- 
ommended rather  for  its  usefulness  in  facilitating  study  than 
for  the  propriety  of  its  classification. 


The  Non-nitrogenized  Bodies. — The  Starch  Group, — 
Starch. — Action  of  Iodine. — Various  Forms  of  Starch. 
— Production  of  Dextrine. — Action  of  Diastase. — Leio~ 
come. — Cane  Sugar. — Glucose. — Distinction  betiveen 
Cane  and  Grape  Sugar. — Milk  Sugar. — Gum. — Dig' 
nine. 

The  non-nitrogenized  bodies,  which  we  shall  first  consid- 
er, are  characterized  by  the  peculiarity  that  they  form  a 
group,  each  member  containing  twelve  atoms  of  carbon, 
united  with  hydrogen  and  oxygen  in  the  proportions  to  form 
water.  They  are,  for  the  most  part,  indifferent  bodies. 


Starch — Fecula  (C'^g^io^io) — found  abundantly  in 
the  vegetable  kingdom,  and  may  be  obtained  from  potatoes 
by  rasping  and  washing  the  mass  upon  a sieve,  the  starch 
being  carried  off  by  the  water.  It  may  also  be  obtained 
from  flour  by  making  it  into  a paste  with  water  and  then 
washing  it.  The  starch  separates,  and  gluten  is  left  behind. 

How  many  carbon  atoms  does  each  member  of  the  amyle  group  contain? 
In  what  proportion  are  their  oxygen  and  hydrogen?  Mention  some  of  the 
chief  bodies  of  this  group.  Frpm  what  sources,  and  in  what  manner,  is 
gtaroh  obtained  ? 


LECTURE  LXIX. 


The  Starch  Group. 


Starch  

Cane  sugar  (crystallized)  .... 


Grape  sugar 
Milk  sugar  . 

Gum  . . . 

Lignine  . . 


VARIETIES  OF  STARCH. 


31$> 

It  is  a white  substance,  commonly  met  with  in  irregular 
prismatic  masses,  which  shape  it  assumes  while  drying.  It 
is  insoluble  in  cold  water,  and  also  in  alcohol,  and  consists 
of  granules  of  difierent  sizes,  as  it  is  derived  from  difi'erent 
plants,  those  of  the  potato  being  about  the  two  hundred  and 
fiftieth  of  an  inch  in  diameter. 

When  starch  is  heated  in  water,  the  covering  membrane 
of  each  granule  bursts  open,  and  the  interior  matter  dis- 
solves  out.  If  the  proportion  of  starch  be  considerable,  the 
whole  forms  a jelly-like  mass,  which  may  be  dried  in  a yel- 
lowish body,  having  the  same  constitution  as  starch  itself. 
Gelatinous  starch  passes  under  the  name  of  Amidine. 

With  free  iodine,  starch  strikes  a deep  blue  color.  When 
water  containing  this  compound  is  heated  to  212°  F.,  the 
color  totally  disappears,  and  is  not  restored  on  cooling ; but 
if  the  source  of  heat  be  removed  as  soon  as  the  color  disap- 
pears, and  before  the  temperature  reaches  212°  F.,  the  color 
returns.  Starch  and  iodine  constitute  an  exceedingly  deli- 
cate test  for  each  other. 

In  commerce,  starch  is  found  under  various  modifications, 
such  as  ArroW'TOot,  Tapioca,  Cassava,  Sago.  It  forms  an 
important  article  of  respiratory  food.  Inuline,  which  is  de- 
rived from  the  dahlia  and  other  plants,  is  a substance  ap- 
proaching starch  in  many  respects. 

When  starch  is  boiled  in  water  with  a small  quantity  of 
sulphuric  acid,  it  changes  into  Dextrine,  a substance  of  the 
same  composition  ; the  acid  being  subsequently  removed  by 
carbonate  of  lime  and  filtration,  that  body  is  procured  on 
evaporation  as  a gummy  mass.  But  if  the  ebullition  be 
continued  for  a longer  time,  the  dextrine  disappears,  and 
grape  sugar  comes  in  its  stead.  Starch  may  also  be  con- 
verted into  grape  sugar  by  the  action  of  a peculiar  ferment, 
Diastase,  which  is  contained  in  an  infusion  of  malt.  Ge- 
latinous starch  may,  in  the  course  of  a few  minutes,  at  160° 
F.,  be  converted  into  dextrine  by  this  substance,  and  soon 
after  into  sugar.  In  either  of  these  cases  the  presence  of 
atmospheric  air  is  not  required ; the  final  action  being  that 
the  starch  simply  assumes  three  atoms  of  water,  and  be- 
comes converted  into  grape  sugar. 


What  is  the  size  of  its  granules  ? What  is  the  effect  of  hot  water  on  it? 
What  is  a amidine  ? What  is  the  action  of  iodine  on  starch  ? Mention 
Borae  other  varieties  of  starch.  How  is  it  converted  into  dextrine  ? How 
into  grape  sugar  ? What  is  diastase  ? What  is  its  action  on  starch  ? 


320 


CANE  SUGAR. GRAPE  SUGAR. 


When  baked  at  a temperature  of  about  400°  F «tarch 
becomes  soluble  in  water,  and  passes  in  commerce  under 
tlie  name  ot  hritisli  Gum,  or  Leiocome. 

Cane  Sugar  + 2HO)  is  found  abundantly  in 

the  juices  oi  many  plants,  and  is  chiefly  extracted  for  coxa- 
mercial  purposes  from  the  sugar-cane,  which,  being  crushed 
between  rollers,  yields  a juice,  which  is  mixed  with  lime 
and  boiled ; a coagulum  having  been  removed  from  it,  it 
IS  rapidly  evaporated,  at  as  low  a temperature  as  possible, 
and  then  crystallized.  In  this  state,  after  a brownish  sir- 
up,  molasses,  has  drained  from  it,  it  passes  in  commerce  un- 
der  the  name  of  Muscovado,  or  brown  sugar.  This  is  pu- 
rifled  by  boiling  in  water  with  albumen,  which,  coagula- 
ting separates  many  of  the  impurities  ; the  solution  is  then 
decolorized  by  animal  charcoal,  evaporated,  solidified  in  co- 
nical vessels,  and,  being  washed  with  a little  clean  sirup 
IS  thrown  into  commerce  as  loaf-sugar.  Sugar  is  also  ob- 
tained from  the  sap  of  the  maple-tree,  and  from  beet-root 
hrom  a strong  solution  sugar  crystallizes  in  rhombic 
prisms,  which  are  colorless  ; they  pass  under  the  name  of 
au gar  Candy.  It  is  soluble  in  one  third  its  weight  of 
cold  water  and  in  any  quantity  of  hot.  It  has  a sweet  and 
proverbially  characteristic  taste.  When  heated,  it  melts 
and  gives  rise  to  a yellowish,  transparent  body,  called  Bar- 
ley b>ugar.  _ But  if  kept  at  a temperature  of  630*^  F.  it 
turns  of  a reddish-brown  color,  constituting  Caramel.  Sutr- 
ar  unites  with  various  bodies,  such  as  lime  and  oxide  of 
lead,  and  with  common  salt  yields  a crystallized  product. 
i3y  caserne  it  is  transformed  into  lactic  acid 

Grape  Sugar-F-mit  Sugar- Glucose-Starch  Sugar 
^“^«^^(^i2^i40u)-is  the  substance  just  de- 
• n arising  lom  the  transmutation  of  starch  under 
the  influence  of  acids.  It  occurs  naturally  in  many  vege- 
table  juices  and  in  honey.  j n 

Compared  with  cane  sugar,  it  is  much  less  soluble  in 
water,  and  less  disposed  to  crystallize.  It  requires  IJ  parts 
of  water  for  so  ution.  It  may  be  distinguished  by  its  action 
with  caustic  alkalies  and  sulphuric  acid,  the  former  turn- 
mg  It  brown,  and  the  latter  dissolving  it  without  blacken- 

^ How  is  Bri'jsh  gum  formed  ? From  what  sources,  and  by  what  means 
IS  cane  sugar  derived?  ^What  are  its  Drooerties  ? Rw  means, 

amel  formed  ? What  is  the  difference  Sn  cane  a^d  gra‘  Bv 

what  test  may  they  be  distinguished  ? ^ ^ 


MILK  SUGAR,  — GUM.— LIGNINE. 


321 


ing,  while  cane  sugar  is  little  acted  on  in  the  former  in* 
stance,  and  blackened  in  the  latter.  The  two  varieties 
may  also  be  distinguished  by  being  mixed  with  a solution 
of  sulphate  of  copper,  to  which,  if  caustic  potash  be  added, 
blue  liquids  are  obtained,  and  these  being  heated,  the  grape 
sugar  throws  down  a green  precipitate,  which  turns  deep 
red,  the  solution  being  left  colorless  : the  cane  sugar  alters 
very  slowly,  a red  precipitate  gradually  forming,  aud  the 
liquid  remaining  blue.  Grape  sugar,  like  cane  sugar,  gives 
with  common  salt  a crystallized  compound.  When  heated 
to  212^  F.  it  loses  two  atoms  of  water,  and  becomes  Cy^ 

Milk  Sugar — Lactine  (^^12-^^12^12) — obtained 
by  evaporating  whey  to  a sirup,  and  the  crystals  which 
then  form  are  to  be  purified  by  animal  charcoal.  It  is  spar- 
ingly soluble,  requiring  five  or  six  times  its  weight  of  wa- 
ter. The  crystals  are  gritty  between  the  teeth.  It  is 
through  the  alcoholic  fermentation  of  this  body  that  the 
Tartars  procure  intoxicating  milk. 

Besides  the  foregoing,  there  are  several  subordinate  vari 
eties  of  sugar,  among  which  may  be  cited 

Ergot  sugar ; 

Eucalyptus  sugar ; 

and  others,  as  liquorice  sugar,  mushroom  sugar,  or  man- 
nite,  &c. 

Gum. — Gum  Arabic  is  obtained  from  several  species  of 
the  mimosa  or  acacia,  from  the  bark  of  which  it  exudes  ; 
is  obtained  in  white  or  yellowish  tears,  of  a vitreous  aspect. 
It  dissolves  in  cold  water,  forming  mucilage,  from  which  it 
may  be  precipitated  pure,  as  Arabine,  by  alcohol. 

Bassorine  is  the  principle  of  Gum  Tragacanth  ; it  does 
not  dissolve  in  water,  but  merely  forms  a jelly  like  mass. 
With  this  substance  should  be  classed  Pectine,  the  jelly 
obtained  from  currants  and  other  fruits.  This  substance 
furnishes  Pectic  acid  by  the  action  of  bases. 

Lignine. — This  substance,  with  Cellulose  and  other  bod- 
ies, forms  the  woody  fibre  or  ligneous  tissue  of  plants.  It 
occurs  in  a state  of  purity  in  the  fibres  of  fine  linen  and 
cotton,  and,  as  is  well  known,  is  of  perfect  whiteness,  insol- 
uble in  water  and  alcohol,  and  tasteless.  Strong  and  cold 

What  are  the  properties  of  milk  sugar?  Mention  some  other  varieties 
of  sugar  ? From  what  source  is  gum  derived  ? What  are  arabine,  basso- 
rine, and  pectine  ? How  may  lignine  be  prepared  ? When  pure,  what  is 
its  color,  and  what  is  its  relation  to  water  ? 

O 2 


I 


322  ACTION  OF  SULPHURIC  ACID  ON  SUGAR. 

sulphuric  acid  converts  it  into  a dextrine,  as  may  be  shown 
by  adding  to  that  substance  pieces  oflinen,  taking  care  that 
the  temperature  does  not  rise  so  as  to  blacken  the  mixture, 
which  is  to  be  w'ell  stirred,  and  suffered  to  stand. for  a time. 
On  dissolving  it  then  in  water,  and  neutralizing  by  the  ad- 
dition of  chalk,  dextrine  is  obtained  ; or  if,  before  neutral- 
izing, the  solution  is  well  boiled,  grape  sugar  is  produced. 


LECTURE  LXX.  j 

Action  of  Agents  on  the  Starch  Group. — Action  of 

Sulphuric  Acid  on  Sugar. — Glucic  Acid  j)roduced  by  ■ 
Lime. — Melassic  Acid. — Action  of  Nitric  Acid. — Pro- 
duction  of  Oxalic  Acid. — Constitution  of  Oxalic  Acid. 

— Its  Salts. — Oxamide. — Saccharic  Acid. — Rhodizon- 
ic  and  Croconic  Acids. — Mucic  Acid. — Xyloidine. — j 

Its  Properties.  | 

In  the  preceding  Lecture  we  have  already  explained  the  | 

change  of  starch  into  sugar,  and  of  ligriine  into  dextrine,  un- 
der the  influence  of  sulphuric  acid  ; and  in  the  vegetable  I 

world  there  can  be  no  doubt  that  these  and  other  similar 
modifications  arise  from  the  action  of  many  causes.  On  in-  j 
specting  the  constitution  of  the  group,  it  will  be  seen  that, 
in  theory,  this  is  to  be  done  by  the  addition  or  abstraction 
of  water. 

When  melted  grape  sugar  is  mixed  with  strong  sulphuric  j 
acid,  and  the  diluted  solution  neutralized  with  carbonate  of 
baryta,  the  sulphosaccharate  of  baryta  is  found  in  the  solu- 
tion. The  Sulphosaccharic  acid  is  a sweetish  liquid,  read-  j 

ily  decomposing  into  sugar  and  sulphuric  acid.  jj 

When,  in  the  process  of  converting  cane  sugar  into  grape  ! 

sugar  by  boiling  with  sulphuric  acid,  the  action  is  long  con-  | 

tinued,  a dark-colored  substance  is  formed,  consisting  of  two  ^ 

different  bodies,  JJlmine  and  TJlmic  Acid,  or,  as  they  are  ' 

termed  by  Liebig,  Sacchulmine  and  Sacchulmic  Acid.  The  I 

latter  is  converted  into  the  former  by  continual  boiling  in  , 

water.  ! 

When  a solution  of  grape  sugar  containing  lime  is  kept 

How  may  lignine  be  converted  into  dextrine  and  crape  si:g-r  ? In  this 
change,  what  is  the  action  impressed  on  the  lignine  ? How  is  sulphosac- 
charic acid  made  ? What  are  sacchulmine  and  sacchulmic  acid  ? 


OXALIC  ACID. 


323 


for  some  time,  the  alkaline  reaction  of  the  lime  finally  dis 
appears  through  the  formation  of  Glucic  Acid,  the  consti- 
tution of  which  is  CqH^O^.  It  is  soluble,  deliquescent,  of 
a sour  taste,  and  yielding,  for  the  most  part,  soluble  salts. 
If  grape  sugar  be  boiled  with  potash  water  until  it  becomes 
black,  a dark  substance  may  be  precipitated  by  an  acid. 
This  is  Melasinic  Acid,  its  constitution  being  Cy^H^O^. 

These  are  some  of  the  less  important  results  of  the  action 
of  acid  and  alkaline  bodies  on  the  starch  group  ; there  are 
others  of  far  more  interest. 

Oxalic  Acid  (CgOg,  HO  -f-  2Aq). — Oxalic  acid  is  form- 
ed by  the  action  of  nitric  acid  on  starch  or  sugar,  or  any 
other  of  the  starch  group,  except  gum  and  sugar  of  milk. 
One  part  of  sugar  is  to  be  mixed  with  five  of  nitric  acid,  di- 
luted with  twice  its  weight  of  water,  and  the  acid  finally 
distilled  off  until  the  residue  will  deposit  crystals  on  cooling. 
These,  being  collected,  are  to  be  purified  by  redissolving 
and  crystallizing.  They  are  oblique  rhombic  prisms,  more 
soluble  in  hot  than  cold  water,  of  an  intensely  acid  taste, 
and  poisonous  to  the  animal  economy,  chalk  or  magnesia 
being  the  antidote.  Oxalic  acid  also  occurs  naturally  in 
several  plants,  in  union  with  potash  or  lime. 

As  the  foregoing  formula  shows,  the  crystals  of  oxalic  acid 
contain  one  equivalent  of  saline  water  and  two  of  water  of 
crystallization.  The  latter  may  be  removed  by  exposure  to 
a low  heat,  the  crystals  then  becoming  a white  powder,  and 
subliming  without  difficulty.  Any  attempt  to  remove  the 
saline  water  and  isolate  the  oxalic  acid  (as  C^O^)  leads  to 
its  decomposition.  Thus,  when  the  acid  is  heated  with  oil 
of  vitriol,  total  decomposition  results;  equal  volumes  of  car- 
bonic oxide  and  carbonic  acid  are  set  free  ; for  the  consti- 
tution of  oxalic  acid  is  such,  that  we  may  regard  it  as  com- 
posed of  an  atom  of  each  of  these  bodies  : 

C203...  = ...C02+  CO; 

and  upon  this  is  founded  one  of  the  methods  of  preparing  car- 
bonic oxide  gas.  The  gaseous  mixture  which  results  from 
the  action  of  the  oil  of  vitriol  is  passed,  as  in  Fig.  250, 
through  a bottle  containing  potash  water,  which  absorbs 
the  carbonic  acid,  and  the  carbonic  oxide  may  be  collected 
at  the  water  trough. 

What  is  the  constitution  of  glucic  acid  ? What  is  the  action  of  potash  on 
grape  sugar?  Describe  the  preparation  of  oxalic  acid.  What  is  the  anti- 
dote to  it?  What  i.s  the  action  of  oil  of  vitriol  on  oxalic  acid  ? 


324 


SALTS  OF  OXALIC  ACID. 


The  production  of  oxalic  acid  from  sugar  by  nitric  acid  is 
due  to  the  replacement  of  hydrogen  by  an  equivalent  quan- 
tity of  oxygen. 

. . +-  ^18  . . + IZgOg ; 

that  is,  one  atom  of  dry  sugar  with  eighteen  of  oxygen  yields 
six  atoms  of  oxalic  acid  and  nine  of  water. 

Salts  of  Oxalic  Acid. 

There  are  three  potash  salts  : 1st.  Neutral  Oxalate  of 
Potash,  made  by  neutralizing  oxalic  acid  with  carbonate 
of  potash  ; crystallizes  in  rhombic  prisms,  soluble  in  three 
times  its  weight  of  water.  ^ 2d.  Binoxaldte  of  Potash, 
made  by  dividing  a solution  of  oxalic  acid  into  two  parts  ; 
neutralize  one  with  carbonate  of  potash,  and  then  add  the 
other.  It  crystallizes  in  rhombic  prisms,  has  a sour  taste, 
and  dissolves  in  forty  parts  of  water.  It  occurs  naturally 
in  several  plants,  as  the  Oxalis  Acetosella.  3d.  Quadroxa^ 
late  of  Potash.  Divide  a solution  of  oxalic  acid  into  four 
]>arts  ; neutralize  one,  and  add  the  rest.  It  crystallizes  in 
octahedrons  ; is  less  soluble  than  either  of  the  foregoing. 
These  salts  are  sometimes  used  for  the  removal  of  ink  stains 
from  linen. 

Oxalate  of  Ammonia,  prepared  by  neutralizing  a hot  so- 
lution of  oxalic  acid  with  carbonate  of  ammonia.  It  crys- 
tallizes in  rhombic  prisms,  which  are  efflorescent.  Its  so- 
lution is  used,  as  has  been  already  stated,  as  a test  and  pre- 
cipitant of  lime.  When  exposed  to  heat  in  a retort,  is  is,  for 
the  most  part,  decomposed  into  water,  ammonia,  carbonic 
acid,  cyanogen,  and  other  compounds ; but  a substance  of 
the  name  of  Oxamide  also  sublimes,  the  constitution  of 
which  is 

C^H^NO^...^...NH^-^2{CO), 

that  is,  containing  the  constituents  of  one  atom  of  amidogen 
and  two  of  carbonic  oxide.  This  remarkable  substance, 
when  boiled  with  potash,  yields,  through  the  decomposition 
of  water,  oxalate  of  potash  and  ammoniacal  gas. 

Oxalate  of  Lime  occurs  naturally,  forming  the  skeleton 
of  many  lichens,  and  is  obtained,  as  has  just  been  said,  by 
precipitating  a lime  salt.  It  is  soluble  in  nitric  acid,  and. 

How  is  oxalic  acid  produced  from  sugar  ? How  many  oxalates  of  pot- 
ash are  there?  How  are  they  prepared?  For  what  purpose  are  the^ 
Balts  sometimes  used?  Under  what  circumstaiices  does  oxamide  forrn? 
What  is  its  constitution  ? 


GUN  COTTON.  325 

Ignited  in  a covered  crucible,  is  converted  into  carbonate  of 
lime. 

Saccharic  Acid  "I"  5iJO) — Oxalhydric  Acid 

— made  by  the  action  of  dilute  nitric  acid  on  sugar.  It  is 
a pentabasic  acid. 

Hhodizo^ic  Acid  +-3J/0),  obtained  by  the  action 

of  potassium  on  carbonic  oxide  at  a red  heat.  When  boiled, 
it  changes  into  Croconic  Acid^  a yellow  body  having  the 
constitution  + HO. 

Mucic  Acid  -}-  %HO),  obtained  by  the  action 

of  dilute  nitric  acid  on  gum  or  sugar  of  milk,  as  in  the  prep- 
aration of  oxalic  acid  by  ether  members  of  the  starch  group. 
It  requires  sixty  times  its  wei^it  of  water  for  solution.  De- 
composed by  heat,  it  yields  pyromucic  acid. 

Xyloidine  ^^5)^  made  by  the  action  of  nitric 

acid,  sp.  gr.  1*5,  on  the  starch,  which  is  converted  into  a 
gelatinous  body,  and  yields  this  substance  as  a white  pre- 
cipitate when  acted  on  by  water.  Its  origin  is  apparent 
from  a comparison  of  its  formula  with  that  of  starch.  Xy- 
loidine is  insoluble  in  boiling  water,  but  by  the  continued 
action  of  nitric  acid  changes  into  oxalic  acid.  100  parts 
of  starch  yield  128  of  xyloidine. 

Gun  Cotton. — Pyroxyline.  A remarkable  compound, 
proposed  as  a substitute  for  gunpowder  by  Schonbein, 
whose  process  for  preparing  it  has  not  yet  been  divulged. 
It  may  be  made  by  the  action  of  monohydrated  nitric  acid 
on  cotton,  paper,  or  sawdust ; and  still  more  conveniently 
by  a mixture  of  nitric  and  sulphuric  acids  on  those  sub- 
stances. 

The  cheapest  and  best  process  for  its  preparation  is  that 
discovered  by  Professor  Ellet,  of  South  Carolina  College 
It  consists  in  soaking  carded  cotton  for  a few  minutes  in  a 
mixture  of  pulverized  nitrate  of  potash  and  oil  of  vitriol, 
washing  the  result  in  hot  water  to  free  the  cotton  from  the 
potash  salt,  and  finishing  the  washing  by  a weak  solution 
of  ammonia.  Gun  cotton  appears  white,  like  ordinary  cot- 
ton, the  fibre  being  little  changed  ; it  is  somewhat  harsh  to 
the  touch  ; when  perfectly  dry,  it  explodes  when  heated  to 
about  300°  F.,  or  by  the  blow  of  a hammer.  It  is  esti- 


Hovv  is  saccharic  acid  made  ? How  is  the  rhodizonate  of  potash  formed  ? 
What  is  its  composition?  How  is  it  changed  into  croconic  acid?  Under 
what  circumstances  does  mucic  acid  form  ? Decomposed  by  heat,  what  does 
mucic  acid  yield  ? How  is  xyloidine  prepared,  and  what  are  its  properties? 


326 


FERMENTATION. 


mated  as  having  about  three  times  the  mechanical  force 
of  gunpowder.  100  parts  of  cotton  yield  about  165  of  gun 
cotton.  It  contains  twice  as  much  nitric  acid  as  xyloidine. 


LECTURE  LXXI. 

On  the  Metamorphosis  of  the  Starch  Group  by  Nitro- 
GENI2ED  Ferments. — Action  of  Leaven. — Bread. — Fer- 
mentation  of  Sugar. — Fermentation  of  Grajpe  Juice. — 
Primary  Action  on  the  JSerment.  — Activity  of  Fer- 
ments due  to  Nitrogen. — Effects  of  Temperature. — Pro- 
duction of  Butyric  Acid. — Ferments  of  different  Prop- 
erties.— Production  of  Wine  and  intoxicating  Liquids. 

In  the  preceding  Lecture  we  have  traced  the  action  of 
the  more  powerful  inorganic  agents  on  the  amyles,  and  seen 
how  a variety  of  bodies  of  different  characters  arise,  some 
of  which,  as  oxalic  acid,  are  of  very  considerable  importance 
But  there  is  another  system  of  changes  which  can  be  im- 
pressed on  this  group  of  bodies,  far  more  curious  in  its  na- 
ture, and  leading  to  far  more  important  results. 

When  flour,  made  into  a paste  with  water,  is  brought  in 
contact  with  Leaven,  that  is  to  say,  a similar  dough,  under- 
going an  incipient  putrefactive  fermentation,  at  a temper- 
ature of  60^  or  70°  F.,  bubbles  of  gas  are  disengaged,  the 
paste  swells  up,  and,  when  baked,  forms  leavened  bread. 
This  ancient  process,  which  is  now  in  use  all  over  the  world, 
depends  on  the  action  of  the  changing  leaven  being  propa- 
gated to  the  sugar  which  the  flour  contains.  The  sugar  is 
resolved  into  alcohol  and  carbonic  acid  gas,  the  former  of 
which  may  be  obtained  by  distilling  the  dough ; and  the 
bubbles  of  the  latter,  entrapped  in  the  yielding  mass,  gives 
to  the  bread  the  lightness  for  which  it  is  prized. 

But  this  process  may  be  better  traced  by  observing  the 
phenomena  of  alcoholic  fermentation  in  the  case  of  pure  sug- 
ar. If  we  take  a solution  of  sugar  in  water,  it  may  be 
kept  for  a length  of  time  without  undergoing  any  change  ; 
but  if  nitrogenized  matters,  such  as  blood,  albumen,  leaven, 
in  a state  of  putrescent  decay,  are  mixed  with  it,  then,  at  a 


What  is  the  action  of  leaven  on  flour?  What  is  the  action  of  decaying 
nitrogenized  matter  on  a solution  of  sugar  ? 


ACTION  OF  FERMENTS* 


327 


temperature  of  70°  F.,  the  sugar  rapidly  disappears,  car* 
boiiic  acid  is  given  off,  and  alcohol  is  Ibund  in  the  solution. 
The  change  is  obvious. 

^ . 2(  C,H,0,)  + 4(CO,) ; 

that  is,  one  atom  of  dry  grape  sugar  yields  two  of  alcohol 
and  four  of  carbonic  acid.  The  final  action,  therefore,  of  the 
ferment  is  to  split  the  sugar  atom  into  carbonic  acid  and  al- 
cohol. 

Of  all  ferments.  Yeast,  for  these  purposes,  is  the  most  pow- 
erful ; it  is  a substance  w’hich  arises  during  the  fermenta- 
tion of  beer.  It  is  probable  that,  in  the  various  sugars,  the 
first  action  is  to  bring  them  into  the  condition  of  grape  sug- 
ar, and  then  the  metamorphosis  ensues. 

By  an  analogous  transformation  of  the  sugar  contained  in 
fruits,  the  dillerent  wines  and  other  intoxicating  liquids  are 
formed  ; thus,  if  we  take  the  expressed  juice  of  grapes  which 
has  not  been  exposed  to  the  contact  of  air,  it  may  be  kept 
for  a length  of  time  without  change  ; but  if  a single  bubble 
of  oxygen  is  admitted  to  it,  fermentation  at  once  sets  in,  the 
grape  sugar  disappears,  and  alcohol  comes  in  its  stead,  car- 
bonic acid  gas  being  disengaged,  and  the  nitrogenized  sub- 
stance, yeast,  deposited.  If  a solution  of  pure  sugar  be  add- 
ed, it  is  involved  in  the  change,  and  portion  after  portion 
will  disappear;  but,  finally,  the  yeast  itself  is  exhausted, 
and  then  any  excess  of  sugar  remains  unacted  upon. 

It  is  obvious  that  the  primary  action  is  an  oxydation  of 
the  ferment,  and  the  moment  its  particles  are  set  in  motion, 
the  motion  is  propagated  to  the  adjacent  body,  the  particles 
of  which  submit  in  succession  ; and  therefore  the  ferment- 
ation is  not  a sudden  action,  but  one  requiring  time.  More- 
over, it  is  plain  that  the  action  is  limited  ; a given  quantity 
of  yeast  will  transmute  only  a definite  quantity  of  sugar. 

The  ferments,  or  bodies  which  possess  this  singular  quality, 
are  nitrogenized  bodies  ; and,  inasmuch  as  non-nitrogenized 
bodies  never  spontaneously  ferment  while  oxydizing,  it  is  to 
the  nitrogen  that  we  are  to  impute  the  qualities  in  question. 

Temperature  has  a remarkable  control  over  ferment  ac- 
tion. The  juice  of  carrots  or  beets,  fermenting  at  50° 

Into  what  bodies  does  the  sugar  atom  split  ? What  is  the  action  of  yeast 
on  sugar?  Describe  the  action  of  yeast  on  grape  juice.  What  is  the  pri- 
mary action  in  these  cases  ? Is  the  action  of  the  ferment  definite  ? To 
what  element  in  the  yeast  is  the  action  due  ? WTat  is  the  effect  of  tem- 
perature on  fermentation  ? 


328 


ACTION  OF  FERMENTS. 


Fahr.,  will  yield  alcohol,  carhonic  acid,  and  yeast ; hut  the 
same  juices,  lermeiituig  at  120°  Fain*.,  produce  lactic  acid, 
gum,  and  maiinite.  Under  these  circumstances,  therefore, 
alcohol  is  the  product  of  lermentation  at  low,  and  lactic 
acid  at  high  teraperature&^! 

But  when  milk  ferments  at  50°  Fahr.,  lactic  acid  is  the 
chief  product,  while  at  80°  Fahr.  the  casein  acts  like  a 
yeast  ferment,  the  milk  sugar  becoming  transformed  into 
grape  sugar,  and  then  resolving  itself  into  alcohol  and  car- 
bonic acid.  In  this  instance  the  action  is  the  reverse  of  the 
former,  lactic  acid  being  the  product  of  a low,  and  alcohol 
of  a high  temperature. 

A very  remarkable  decomposition  takes  place  when  casein 
ferment  acts  on  sugar  at  80°  Fahr.  in  presence  of  carbon- 
ate of  lime.  Under  these  circumstances,  carbonic  acid  gas 
and  hydrogen  are  evolved,  and  Butyric  Acid  appears.  On 
comparing  the  constitution  of  butyric  acid  with  alcohol,  it 
will  be  seen  that  the  latter  contains  the  elements  of  the  for- 
mer, with  an  excess  of  hydrogen  ; so  that,  duriiig  this  fer- 
mentation, the  alcohol  atom  is  divided. 

All  ferments  possess  certain  properties  in  common,  but 
each  has  its  specific  powers  ; and  the  products  which  are 
evolved  difier  in  diflerent  cases.  Most  commonly  the  ac- 
tivity of.  these  bodies  is  excited  by  an  incipient  oxydation, 
the  result  of  wdiich  would  be  to  bring  the  ferment  itself  to 
a simpler  constitution.  In  this  respect,  therefore,  the  first 
stage  of  fermentation  is  a combustion  at  common  tempera- 
tures, or  an  eremacausis  of  the  ferment  itself ; but  this  ac- 
tion is  speedily  propagated  to  the  surrounding  mass,  which 
becomes  involved  in  the  change.  Whatever,  therefore,  pre- 
vents the  incipient  oxydation  of  the  ferment,  puts  a stop  to 
the  whole  process.  By  raising  their  temperature  to  212°, 
and  then  cutting  off  the  access  of  air,  substances  which 
would  otherwise  undergo  a very  rapid  change  may  be  kept 
for  any  length  of  time  without  alteration.  On  this  princi- 
ple, meats,  milk,  and  other  viands  may  be  preserved. 

We  have  now  pointed  out  the  peculiarities  of  ferment  ac- 
tion, showing  that  two  successive  stages  may  be  traced  in 
the  process  ; the  first  arising  in  the  oxydation  of  the  fer- 

Describe  the  causes  of  tbe  fermentation  of  vegetable  juices  and  of  milk  ? 
Under  what  circumstances  does  butyric  acid  form?  What  is  the  change 
■which  the  ferment  itself  undergoes  ? What  is  the  effect  of  cutting  off  the 
access  of  air  ? What  are  the  two  stages  of  ferment  action  ? 


PREPARATION  OF  WINES. 


meiit,  by  which  its  molecules  are  decomposed ; and  the 
second,  which  consists  in  the  propagation  of  this  movement 
to  the  surrounding  particles,  upon  which  changes  are  im- 
pressed, the  nature  of  which  differs  with  the  temperature 
and  the  specilic  action  of  the  ferment  itself. 

Wine  is  made  from  the  expressed  juice  of  grapes,  which, 
containing  a nitrogenized  body,  albumen,  when  exposed  to 
the  air  undergoes  spontaneous  fermentation  ; the  course  of 
the  action  being,  1st.  The  oxydation  of  the  vegetable  albu- 
men ; 2d.  The  propagation  of  its  action  to  the  grape  sugar. 
If  the  sugar  is  in  excess,  the  wine  remains  sweet ; il‘  the 
albumen  is  in  excess,  the  wfne  is  dry.  The  wine,  as  soon 
as  the  first  action  is  over,  is  removed  into  casks.  During 
these  changes,  the  bitartrate  of  potash,  which  exists  natur- 
ally in  grape  juice,  and  which,  though  sparingly  soluble  in 
water,  is  much  less  so  in  alcohol,  is  deposited.  It  goes  un- 
der the  name  o^Argol.  Most  other  fruit  juices  contain  free 
acid,  such  as  malic  or  citric  ; and  hence  good  wine  can  not 
be  made  from  them,  because,  if  all  the  sugar  is  removed, 
they  possess  a sharp  taste  ; and  if,  as  is  commonly  the  case, 
a portion  is,  left  to  correct  the  acidity,  it  is  liable  to  run  into 
a second  fermentation. 

. Inferior  liquids,  such  as  cider,  perry,  &c.,  are  made  from 
other  vegetable  juices,  as  those  of  apples,  pears,  &c.  Beer, 
porter,  and  ale  are  made  from  an  infusion  of  malt,  which  is 
barley,  a portion  of  the  starch  of  which  is  transposed  into 
sugar  by  partial  germination.  The  principles  of  the  fer- 
mentation are,  in  all  these  instances,  the  same. 


LEOTUIIE  LXXII. 

On  the  Derivatives  of  Fermentative  Processes. — 
Alcohol. — Its  Propei'ties. — Exists  in  Wines, — Lactic 
Acid. — Production  and  Properties. — Sulphuric  Ether. 
— Its  Distillation. — The  Ethyle  Series. — Chloride. — 
Bromide. — Nitrate,  cj-c. — (Enanthic  Ether. 

ALCOHOL  {Hydrated  Oxide  of  Ethyle) 

By  \he  distillation  of  wine,  or  aiiy  other  fermented  sac- 

What  is  the  process  for  the  making  of  winp  ? When  is  the  wine  sweet 
and  when  dry  ? What  is  argol  ? Why  are  other  fruit  juices  less  propei 
for  making  wine  than  grape  juice  ? How  is  alcohol  procured  ? 


330 


LACTIC  ACID. 


charine  juice,  spirits  of  wine  may  be  obtained.  As  first  pre- 
pared, it  contains  a large  quantity  of  water,  which  comes 
over  with  it.  This  product  being  rectified,  and  the  first  por- 
tion preserved,  yields  a spirit  containing  twelve  to  fifteen 
per  cent,  of  water.  By  putting  this  into  a retort  with  half 
its  weight  of  quicklime,  keeping  the  mixture  a few  days, 
and  then  distilling  at  a low  temperature,  absolute  or  anhy- 
drous alcohol  is  obtained. 

Anhydrous  alcohol  is  a colorless  liquid,  of  a burning  taste 
and  pleasant  odor.  Its  specific  gravity,  at  60°  F.,  is  0*795. 
It  boils  at  173°  F.,  and  at  a still  lower  point  if  slightly  diluted 
with  water,  though  the  boiling  point  rises  if  the  water  be  in 
greater  proportion.  It  has  not  been  yet  frozen.  The  spe- 
cific gravity,  also,  varies  with  the  amount  of  water  present ; 
and  hence  the  purity  of  spirits  of  wine  may  be  determined 
by  ascertaining  its  density.  Alcohol  is  very  inflammable, 
burns  with  a pale  blue  flame,  with  the  production  of  car- 
bonic acid  gas  and  water.  It  is  much  used  in  chemical  in- 
vestigations as  furnishing  a lamp  flame  free  from  smoke, 
and  as  possessing  an  extensive  range  of  solvent  powers,  act- 
ing upon  resins,  oils,  and  other  bodies,  which  arq  not  acted 
upon  by  water. 

The  strong  wines,  such  as  port  and  sherry,  contain  from*, 
nineteen  to  twenty-five  per  cent,  of  alcohol ; the  light  win& 
from  twelve  per  cent,  upward ; and  beer,  porter,  &c.,  from 
five  to  ten  per  cent. 

Lactic  Acid  Fermentation. — We  have  already  seen  that 
vegetable  juices  as  well  as  milk  will,  under  certain  cir- 
cumstances of  temperature,  yield,  during  fermentation,  lac- 
tic acid  instead  of  alcohol.  This  acid  may  therefore  be 
made  by  dissolving  a quantity  of  sugar  of  milk  in  milk,  put- 
ting it  in  a warm  place,  and  allowing  it  to  turn  sour  spon- 
taneously. A part  of  the  casein  of  the  milk  here  acts  as 
the  ferment,  and  as  lactic  acid  is  set  free,  it  coagulates  the 
rest  and  mak-es  it  insoluble.  By  the  addition  of  carbonate 
of  soda,  to  neutralize  the  acid,  this  is  prevented,  and  the 
ferment,  resuming  its  activity,  produces  more  lactic  acid. 
When,  by  this  process,  all  the  sugar  is  exhausted,  the  liquid 
is  boiled,  filtered,  evaporated  to  dryness,  and  the  lactate  of 

How  may  it  be  obtained  anhydrous  ? What  are  its  properties  ? How 
may  the  strength  of  spirits  of  wine  be  determined  ? For  what  purposes  is  it 
used  in  chemistry  ? How  much  alcohol  per  cent,  is  contained  in  port, 
iherry,  beer,  and  ale  ? 


LACTIC  ACID. 


LTMKK.  331 

soda  dissolved  out  by  hot  alcohol.  From  this  alcoholic  so- 
luUon  the  acid  may  be  obtained  by  precipitating  the  soda 
by  sulphuric  acid. 

Lactic  Acid  {C is  obtained  as  a sirupy  so- 
lution by  concentrating  in  a vacuum  over  oil  of  vitriol.  It 
is  colorless,  has  a specific  gravity  of  1 -215,  is  very  sour,  and 
soluble  in  water  and  alcohol.  It  yields  a complete  series 
of  salts,  most  of  which  are  soluble.  Among  these  salts,  the 
most  interesting  are  those  of  lime  and  of  zinc. 

Ether — S'ldphuric  Lther — Oxide  of  Ethyle 
— Ether  is  prepared  by  distilling  equal  weights  of  alcohol 
and  oil  of  vitriol,  receiving  the  resulting  vapor  in  a Liebig’s 
condenser,  a d h c,  as  in  Fig,  275,  the  condenser  being  cool- 


ed by  water  from  the  reservoir,  z,  flowing  into  the  funnel,  6*, 
the  waste  passing  into  the  vessel,  5,  and  the  ether  distilling 
into  the  bottle,  e.  The  process  is  to  be  stopped  as  soon  as 
the  mixture  begins  to  blacken.  The  first  product  may  be 
rectified  by  redistillation  from  caustic  potash. 

Ether  is  a colorless  and  limpid  liquid,  of  a peculiar  odor 
and  hot  taste.  It  boils  at  96"^  F.,  and  has  not  yet  been 
frozen.  Its  specific  gravity,  at  60^  F.,  is  ’720.  It  volatil- 
izes with  rapidity,  and  therefore  produces  cold.  It  is  com- 

Vrhat  is  the  process  for  obtaining  lactic  acid  ? V/hat  is  its  constitution? 
What  are  its  properties  ? How  is  ether  made  ? What  are  the  properties 
of  ether  ? 


COMPOUNDS  OF  ETHYLE. 


Sd2 


bnstible,  and  burns  with  the  evolution  of  much  more  light 
than  alcohol.  The  specific  gravity  of  its  vapor  is  2 586. 
■VYith  oxygen  or  atmospheric  air  it  forms  an  explosive  mix- 
ture, and,  kept  in  contact  with  air,  it  becomes  acid  from  the 
plod  action  ot  acetic  acid.  It  dissolves  in  alcohol  in  ail  pro- 
portions, but  ten  parts  of  Avater  are  required  to  dissolve  one 
of  it ; it  also  dissolves  many  fatty  substances,  and  hence  is 
of  considerable  use  in  organic  chemistry. 

Ether  is  regarded  as  the  oxide  of  an  ideal  compound  rad- 
ical, ethyle,  Avhich  gives  rise  to  a series  of  other 

bodies. 

T/ie  Ethyle  Group. 

Ethyle,  C^Ef^ :r:z: 

Oxide  of  ethyle = Ae,  O. 

Hydrated  oxide = Ae,  O 4-  HO. 

Chloride  of  ethyle  . . . . = Ae,  Cl. 

Bromide  “ ....=:=  Ae,  B. 

Nitrate  “ ....=.  Ae,  04-  NO.. 

Hyponitnte  “ . . . . ==  Ae,  O 4-  NO.. 

&c. 

The  oxide  of  ethyle,  as  has  just  been  stated,  is  ether  it- 
self The  hydrated  oxide  is  alcohol. 

Chloride  of  ^ Ethyle — Hydrochloric  Ether — may  be 
made  by  saturating  rectified  spirits  of  Avine  with  dry  hydro- 
chloric acid  gas,  and  distilling  the  result  at  a low  temper- 
ature, conducting  the  A^apor  through  a bottle  of  Avarm  wa- 
ter, and  then  condensing  in  a receiA^er  surrounded  by  a 
freezing  mixture.  It  is  a colorless,  volatile  liquid,  of  a pe- 
cuhar  aromatic  smell;  the  specific  gravity  is  *874.  It 
boils  at  52^,  and  is  not  decomposed  by  nitrate  of  silA^’er. 

Bromide  of  Etlujle  {Hydrobromic  Ether)  and  Iodide 
of  Ethyle  {Hydriodic  Ether)  are  not  of  any  importance  ; 
and  the  same  remark  may  be  made  as  respects  the  suhohu- 
ret  and  the  cya7iide. 

Niti'ate  of  Ethyle — Nitric  Ether — may  be  made  on  the 
small  scale  by  distilling  equal  weights  of  alcohol  and  nitric 
acid  with  a small  quantity  of  nitrate  of  urea.  The  latter 
substance  is  used  to  prevent  the  nitric  acid  deoxydizing, 
and  giving  rise  to  the  production  of  hyponitrite  instead  of 
nitrate  of  ethyle.  Nitrate  of  ethyle  is  insoluble  in  water 
has  a density  of  boils  at  185°,  and  has  a sweet 

taste.  Its  vapor  explodes  when  heated. 


Is  ether  soluble  in  water?  What  elass  of  bodies  does  it  dissolve  ’ Of 
what  substance  is  it  an  oxide  ? What  is  the  true  name  of  hydrochloric 
ether,  and  how  is  it  prepared  ? How  is  the  nitrate  of  ethyle  ? 


COMPOUNDS  OF  ETHYLE. 


333 


Hyjoonitrite  of  Ethyle — Nitwits  Ether  {AeO,  NO^). — 
This  ether  may  be  made  by  passing  the  hyponitrous  acid, 
disengaged  from  one  part  of  starch  and  ten  of  nitric  acid, 
through  alcohol,  diluted  with  half  its  weight  of  water  and 
kept  cold.  It  is  a yellowish,  aromatic  liquid,  having  the 
odor  of  apples.  It  boils  at  62°  F.  Its  density  is  *967. 
The  sweet  spirits  of  nitre  is  a solution  of  this  ether  with  al- 
dehyde and  other  substances  in  alcohol. 

Carbonate  of  Ethyle — Carbonic  Ether  [AeO,  CO^. — 
made  by  the  action  of  potassium  on  oxalic  ether,  and  distil- 
lation of  the  product  with  water.  It  floats  on  the  surface  of 
the  distilled  liquid,  is  an  aromatic  liquid,  and  boils  at  259®. 

Oxalate  of  Ethyle — Oxalic  Ether — prepared  by  distil- 
ling four  parts  of  binoxalate  of  potash,  five  of  sulphuric  acid, 
and  four  of  alcohol  into  a warm  receiver.  The  product  is 
washed  with  water  to  separate  any  alcohol  *or  acid,  and  re- 
distilled. It  is  an  oily  liquid,  of  an  aromatic  odor  ; it  boils 
at  353°  F.,  and  is  slightly  heavier  than  water.  With  an  ex- 
cess of  ammonia  it  yields  Oxamide  and  alcohol.  With  a 
smaller  proportion  of  ammonia  and  alcohol  it  yields  Oxa- 
methane,  CqH^NO^. 

Acetate  of  Ethyle — Acetic  Ether  {AeO,  and 

Formiate  of  Ethyle — Formic  Ether  l^AeO,  C^NO^ — 
are  procured  in  a similar  manner  with  the  foregoing,  substi- 
tuting in  one  case  acetate  of  potash,  and  in  the  other  for- 
miate of  soda. 

CEnanthic  Ether  {AeO,  is  prepared  from  an 

oily  liquid  which  passes  over  during  the  distillation  of  cer- 
tain wines.  It  has  a powerful  vinous  odor,  is  a colorless 
liquid,  specific  gravity  '862  ; it  boils  at  410°  F.,  dissolves 
readily  in  alcohol,  and  gives  their  peculiar  aroma  to  the 
wines  in  which  it  is  found.  From  it  oenanthic  acid  may  be 
obtained  by  the  successive  action  of  potash  and  sulphuric 
acid.  It  is  an  oily  body,  becoming  a soft  solid  at  55®  F. 

How  is  nitrous  ether  prepared,  and  what  are  its  properties  ? How  are 
carbonic  ether,  acetic  ether,  and  formic  ether  made  ? From  what  source  is 
cenanthic  ether  derived  ? What  is  its  relation  to  various  bodies  ? 


334  SULPHOVINIC  AND  PHOSPHOVINIC  ACIDS. 


LECTURE  LXXIII. 

Derivative  Bodies  of  Alcohol. — Sulphovinic  and  Phos- 
phovinic  Acids. — Products  of  Sulphovinic  Acid  at  dif 
f event  Boiling  Points. — The  continuous  Ether  Process. 
— The  continuous  Olefiant  Gas  Process. — Dutch  Li- 
quid.  — Successive  Substitutions  of  Chlorine  in  it. — 
Heavy  and  Light  Oil  of  Wine. — Sulphate  of  Carhyle 
and  its  derivative  Acids. 

Sulphovinic  Acid — Bisulphate  ofEthyle  .2S 

O3  + HO). — A mixture  of  sulphuric  acid  with  an  equal 
weight  of  alcohol  is  to  be  heated  to  the  boiling  point,  and 
then  allowed  to  cool.  It  is  then  to  be  diluted  with  water 
and  neutralized  with  carbonate  of  baryta  ; the  sulphate  of 
baryta  subsides.  The  solution  is  then  filtered,  evapora- 
ted, and,  when  cold,  the  sulphovinate  of  baryta  crystallizes. 
From  this  the  sulphovinic  acid  may  be  obtained  by  precip- 
itating the  baryta  with  dilute  sulphuric  acid,  and  evapor- 
ating the  resulting  solution  in  vacuo.  It  is  a sirupy  liquid, 
of  a sour  taste,  giving  rise  to  a series  of  soluble  salts,  which 
decompose  at  the  boiling  point,  as  will  be  presently  seen. 

Phosphovinic  Acid  {C^H^O,  PO5  + 2HO)  is  made  on 
the  same  principles  as  the  foregoing,  phosphoric  acid  being 
substituted  for  sulphuric,  and  decomposing  the  resulting  ba- 
ryta salt  in  the  same  way.  It  is  a sirupy  liquid,  of  a sour 
taste,  and  dissolves  in  water,  alcohol,  and  ether  very  readily. 
It  is  decomposed  by  heat. 

If  sulphovinic  acid  be  diluted  so  as  to  bring  its  boiling 
point  below  260°  F.,  it  is  resolved  at  that  temperature  chief- 
ly into  sulphuric  acid  and  alcohol,  which  distills  over. 

If  the  boiling  point  is  from  260^^  F.  to  310°  F.,  the  distil- 
lation results  chiefly  in  the  production  of  hdyrated  sulphuric 
acid  and  ether. 

If,  by  the  addition  of  sulphuric  acid,  the  boiling  point  is 
carried  above  320°  F.,  the  action  is  more  complex,  but  the 
chief  product  which  passes  over  is  olefiant  gas. 

How  is  sulphovinic  acid  made  ? What  is  its  compositipn  ? What  is  the 
composition  and  mode  of  preparation  of  phosphovinic  acid  ? Wliat  is  the 
result  of  the  exposure  of  sulphovinic  acid  at  different  boiling  points  ? 


CONTINUOUS  ETHER  PROCESS. 


335 


The  ordinary  method  of  preparing  ether  is,  therefore,  ob- 
viously very  disadvantageous,  because  it  is  only  within  a 
particular  range  of  temperature  that  that  body  is  evolved. 
At  first  the  low  temperature  yields  alcohol,  and  as  the  heat 
rises,  the  mixture  begins  to  blacken,  and  olefiant  gas  to  bo 
evolved. 

To  obviate  these  difficulties,  a very  beautiful  process, 
the  continuous  process,  has  been  introduced.  It  consists  in 
taking  a mixture  of  eight  parts  by  weigh t%f  sulphuric  acid 
and  five  of  alcohol,  specific  gravity  *834,  the  boiling  point 
of  which  is  about  300^  F.  This  is  brought  to  that  temper- 
ature, and  alcohol  of  the  same  density  is  allowed  slowly  to 
flow  into  the  mixture,  the  boiling  point  being  steadily  kept 
as  near  300°  F.  as  possible,  and  the  mixture  maintained  in 
a state  of  violent  ebullition.  Water  and  ether  distill  over 
together,  and  may  be  passed  through  a Liebig’s  condenser ; 
they  collect  in  the  receiver  in  separate  strata,  or,  if  thiy 
does  not  take  place  at  first,  the  addition  of  a little  water  in 
the  receiver  insures  it. 

In  this  manner  a very  large  quantity  of  alcohol  may  be 
converted  into  ether  and  water  by  the  action  of  a limited 
amount  of  sulphuric  acid  ; and  in  a similar  manner,  by  ad- 
justing the  boiling  point  so  as  to  be  between  320°  and 
330°  F.,  olefiant  gas  may  be  continuously  obtained.  All, 
therefore,  that  is  required,  is  to  CQnvey  the  alcoholic  vapor 
through  a mixture  of  oil  of  vitriol  with  half  its*  weight  of 
water,  which  has  the  required  boiling  point.  In  this  pro- 
cess the  acid  does  not  blacken,  and  it  is  therefore  much 
more  advantageous  than  that  described  for  the  preparation 
of  olefiant  gas  in  Lecture  LV. 

Cloride  of  Olefiant  Gas — Dutch  Liquid  — 

is  prepared  by  mixing  equal  volumes  of  chlorine  and  olefiant 
gas  in  a large  glass  globe.  It  is  a colorless  and  fragrant 
liquid,  soluble  in  alcohol  and  ether,  but  less  so  in  water. 
It  boils  at  180°  F.,  and  when  acted  on  by  a solution  of  caus- 
tic potash  in  alcohol,  it  yields  chloride  of  potassium  and  a 
substance  which,  on  being  cooled  by  a freezing 

mixture,  condenses  into  a liquid.  This  liquid,  brought  in 
contact  with  chlorine,  absorbs  that  substance,  and  yields  a 
new  compound,  C^H^Cl,  which  may  again  be  decomposed 

Describe  the  continuous  process  for  the  preparation  of  ether.  Describe 
the  continuous  process  for  preparing  olefiant  gas.  How  is  Dutch  liquid  pre 
pared  ? 


836 


SUBSTITUTIONS  IN  DUTCH  LiaUID. 


|jy  an  alcoholic  solution  of  potash  into  chloride  of  potassium 
and  a new  volatile  body, 

There  is  an  iodide  and  a bromide  of  olefiant  gas,  which 
possess  a constitutiqn  analogous  to  the  chloride. 

When  chlorine  gas  is  made  to  act  upon  Dutch  liquid, 
three  different  substances  may  he  successively  formed  by  the 
gradual  abstraction  of  hydrogen,  and  its  equivalent  substi- 
tution by  chloriim.  These  substances  are  as  follow  : 

Dutch  liquid 

(1.) CiH^Ch. 

(2.) 

v3.) Ck. 


The  first  and  second  of  these  products  are  volatile  liquids, 
the  third  is  the  perchloride  of  carbon,  in  which  it  appears 
that  all  the  four  atoms  of  hydrogen  in  the  Dutch  liquid  have 
been  removed,  and  their  places  occupied  by  four  atoms  of 
chlorine.  This  perchlo7'ide  of  carbon  is  a white  crystalline 
body,  soluble  in  alcohol  and  ether.  Its  melting  point  is 
320°  F.  By  passing  its  vapor  through  a red-hot  porcelain 
tube,  it  is  decomposed,  yielding  and  free  chlorine, 

and  this  again  gives  rise  to  subchloride  of  carbon^ 
by  being  passed  through  an  ignited  porcelain  tube  at  a white 
heat.  The  former  of  these  bodies  is  a colorless  liquid,  and 
the  latter  a silky  solid. 

Heavy  Oil  cf  Wine  2SO^  may  be  procured 

by  the  destructive  distillation  of  sulphovinate  of  lime,  or  by 
distilling  two  and  a half  parts^  of  oil  of  vitriol  and  one  of 
spirit  of  wine.  It  is  a colorless  liquid,  heavier  than  water, 
and  having  an  odor  of  peppermint.  Boiled  with  water,  it 
yields  sulphovinic  acid,  and  Light  or  Siveet  Oil  of  Wine, 
a substance  which,  after  standing  a few  days,  deposits  white 
‘inodorous  crystals  of  Ltherine,  The  residue,  which 

still  remains  liquid,  is  Etherole,  C^H^.  It  is  a yellowish 
liquid,  lighter  tlian  water,  and  soluble  in  alcohol  and  ether. 

Sulphate  of  Carbyle  djSOg)  arises  when  the  va- 

por of  anhydrous  sulphuric  acid  is  absorbed  by  pure  alcohol, 
it  is  a white  crystalline  body.  When  dissolved  in  alcohol 
and  water  added,  the  solution  neutralized  by  carbonate  of 
baryta,  filtered,  concentrated,  and  then  mixed  with  alcohol, 


What  is  the  nature  of  the  series  of  bodies  arising  from  the  action  of  chlo- 
rine on  Dutch  liquid?'  Under  what  circumstances  does  the  heavy  oil  of 
wiiie  form  ? How  is  sweet  oil  of  wine  prepared  ? What  are  etherine  and 
etherole  ? When  the  vapor  of  anhydrous  sulphuric  acid  is  passed  into  pure 
alcohol,  what  is  the  result  ? 


OXYDATION  OF  ALCOHOL. 


337 


the  Ethionate  of  Baryta  precipitates.  This,  when  decom- 
posed by  dilute  sulphuric  acid,  yields  Hydrated  Ethionic 
Acid,  the  constitution  of  which  is  diSOgd-  2HO. 

Ethionic  acid  yields  a series  of  salts,  many  of  which  can  be 
obtained  in  crystals.  On  being  boiled,  solution  of  ethionic 
acid  yields  sulphuric  acid  and  Isethionic,  the  peculiarity  of 
which  is,  that  it  is  isomeric  with  sulphovinic  acid,  both  con* 
taining  280^  + HO. 


LECTURE  LXXIV. 

OxYDATioN  OF  Alcohol. — TheAcetyle  Group. — Aldehyde. 
— lU  Preparation  and  Properties.  — Aldehydic  Add. 
— Davy's  Flameless  Lamp. — Acetal  produced  by  Pla- 
tinum Black. — Acetic  Acid,  Production  of. — Nature 
of  the  Change  from  Alcohol  to  Acetic  Acid. — 8alts  of 
Acetic  Acid. 

It  has  been  already  stated  (Lecture  LXXIL),  that  when 
alcohol  is  burned  in  contact  with  oxygen  gas  or  atmospheric 
air,  the  sole  products  of  the  combustion  are  carbonic  acid 
gas  and  water.  But  when  the  oxydation  is  partial,  the  hy- 
drogen is  removed  by  preference,  and  a new  series  of  bodies 
is  the  result,  designated  as 


The  Acetyle  Series. 

Acetyle,  = Ac. 

Oxide  of  acetyle . . . =AcO. 

Hydrated  oxide  of  acetyle  (aldehyde)  . . = AcO  -j-  HO. 

Acetylous  acid  (aldehydic  acid)  .... 

Acetic  acid = AcOa  -{-  HO. 


Acetyle  is  an  ideal  body,  dilTering  from  ethyle  by  con- 
taining only  three  atoms  of  hydrogen  instead  of  five.  Its 
oxide,  also,  has  not  yet  been  insulated. 

Hydrated  Oxide  of  Acetyle — Aldehyde — may  be  obtain- 
ed by  distilling  two  parts  of  the  compound  of  aldehyde  and 
ammonia,  dissolved  in  two  parts  of  water,  with  a mixture 
of  three  of  oil  of  vitriol  and  four  of  water,  and  redistilling 
the  product  from  chloride  of  calcium  at  a low  temperature. 
It  is  a colorless  liquid,  of  a suffocating  odor.  Its  density  is 
790,  its  boiling  point  72^  F.  It  is  soluble  in  water  and 

How  are  ethionic  and  isethionic  acids  prepared?  What  is  acetyle T 
How  is  aldehyde  prepared  ? What  are  its  properties  ? 

P 


338 


ALDEHYDE. ACETAL. 


alcohol.  It  slowly  oxydizes  in  the  air,  and  more  rapidly 
under  the  influence  of  the  black  powder  of  platinum,  pro- 
ducing acetic  acid.  Heated  with  caustic  potash,  it  yields 
aldehyde  resin,  a brown  body  of  a resinous  aspect.  Alde- 
hyde has  received  its  name  from  the  circumstance  that  it 
contains  the  elements  of  alcohol  minus  two  atoms  of  hydro- 
gen {Alcohol  Dehydrogenatus). 

When  pure  aldehyde  is  kept  for  a length  of  time  at  32^ 
F.  in  a close  vessel,  it  yields  JEllcddchydc^  a substance  iso- 
meric with  itself,  but  possessing  different  properties,^  the 
specific  gravity  of  its  vapor,  for  example,  being  three  times 
that  of  the  vapor  of  aldehyde.  From  it  there  is  also  pro- 
duced, at  common  temperatures,  a second  isomeric  body, 
Metaldehydc.  ^ _ -j 

Aldehydic  Acid  may  be  obtained  by  digesting  oxide  of 
silver  with  aldehyde,  and  precipitating  the  metal  with  sul- 
phureted  hydrogen.  It  contains  one 
atom  of  oxygen  less  than  acetic  acid, 
and  is  one  of  the  products  of  the  slow 
combustion  of  ether  in  Davy’s  flameless 
lamp,  which  may  be  made  by  putting 
a small  quantity  of  ether  in  a jar  {Fig, 
276),  and  suspending  in  the  vapor,  as  it 
mixes  with  atmospheric  air,  a coil  of 
platina  wire  which  has  receiitly  been 
ignited.  The  wire  remains  incandes- 
cent as  long  as  any  ether  is  present. 
The  same  result  is  obtained  by  putting 
a spiral  of  platina  wire,  or  a ball  of  spongy  platina,  over 
the  wick  of  a spirit  lamp,  the  lamp  being  lighted  for  a snort 
time,  and  then  blown  out ; the  platinum  continues  incandes- 
cent, evolving  a peculiarly  acrid  vapor. 

Acetal  containing  the  elements  of  ether  and 

aldehyde,  is  produced  by  the  oxydation  of  vapor  of  alcohol 
by  black  powder  of  platinum,  the  alcohol  being  placed  in  a 
jar,  with  moistened  platinum  black  in  a capsule  above  it. 
In  the  course  of  several  days  the  alcohol  will  be  found  to 
have  become  sour  ; it  is  then  to  be  neutralized  with  chalk 
and  distilled.  Chloride  of  calcium  separates  an  oily  liquid 


Fig,  276. 


From  what  is  the  name  of  aldehyde  derived?  Under  what  circumstan- 
ces do  elaldehydc  and  metaldehyde  form  ? What  is  Davy  s tameless  .amp 
Mention  some  of  its  products.  What  is  the  constitution  of  acctai . 
rhay  it  be  prepared  by  platinum  black  ? 


ACETIC  ACID. 


339 


from  the  distilled  product.  This,  on  being  distilled  at  a 
temperature  of  200°  F.,  yields  acetal.  It  is  a colorless  and 
aromatic  liquid,  lighter  than  water,  and  boiling  at  203° 
F.  It  yields,  under  the  influence  of  an  alcoholic  solution  of 
caustic  potash,  by  absorbing  oxygen  from  the  air,  resin  of 
aldehyde. 

Acetic  Acid — Pyroligneous  Acid — Vinegar 
+ HO). — When  dilute  alcohol  is  dropped  on  platina  black, 
oxydation  takes  place,  and  the  vapors  of  acetic  acid  are 
formed.  On  the  large  scale  it  is  also  Fig.  277. 
formed  by  allowing  a mixture  of  alcohol, 
water,  and  a small  quantity  of  yeast, 

Fig.  277,  to  flow  over  wood  shavings 
which  have  been  steeped  in  vinegar  con- 
tained in  a barrel  through  which  atmos- 
pheric air  is  allowed  to  circulate  by  the 
apertures  c,  c,  c.  The  temperature  rises, 
and  the  acetification  goes  on  with  rapidity, 
the  product  being  collected  in  the  receiver, 
d.  Vinegar,  also,  is  formed  by  the  spontaneous  souring  of 
wines  or  beer  containing  ferment,  and  kept  in  a cask  to 
which  atmospheric  air  has  access.  During  the  destructive 
distillation  of  dry  wood,  acetic  acid  (hence  called  pyrolig- 
neous acid)  in  an  impure  state  is  found  among  the  products. 

The  strongest  acetic  acid  may  be  made  by  distilling  pow- 
dered anhydrous  acetate  of  soda  with  three  times  its  weight 
of  oil  of  vitriol.  The  product  is  then  re-distilled,  and  ex- 
posed to  a low  temperature,  when  crystals  of  hydrated  acetic 
acid  form ; the  fluid  portion  is  poured  off,  and  the  crystals 
suffered  to  melt.  It  is  a colorless  liquid,  which  crystallizes 
below  60°  F.  ; has  a very  pungent  odor,  and,  placed  on  the 
skin,  blisters  it ; boils  at  248°  F.,  the  vapor  being  inflam- 
mable. It  dissolves  in  water,  alcohol,  and  ether  ; and  in  a 
less  pure  state,  as  vinegar,  its  taste,  odor,  and  applications 
are  well  known.  If  its  constitution  be  compared  with  that 
of  alcohol, . 

Alcohol 

Acetic  acid 

it  is  seen  to  differ  from  that  substance  in  the  circumstance 
that  two  hydrogen  atoms  have  been  removed  from  the  al- 

Mention  some  of  the  different  methods  by  which  acetic  acid  may  be  made. 
Why  is  it  sometimes  called  pyroligneous  acid  ? What  change  does  alcohol 
undergo  in  passing  into  acetic  acid  ? 


340 


SALTS  OF  ACETIC  ACID. 


cohol,  and  their  places  taken  by  two  oxygen  atoms.  Hence 
the  various  processes  for  its  production  are  easily  explained. 
Acetic  acid  gives  rise  to  several  important  salts. 

Acetate  of  Potash  (7fO,  C^TTgOg)  is  obtained  by  neutral- 
izing acetic  acid  with  carbonate  of  potash,  evaporating  to 
dryness,  and  fusing.  This  salt  is  very  deliquescent,  and  has 
an  alkaline  reaction. 

Acetate  of  Soda  is  made  on  the  large  scale  by  saturating 
the  impure  pyroligneous  acid  formed  in  the  destructive  dis- 
tillation of  wood,  with  lime,  and  then  decomposing  the  ace- 
tate of  lime  with  sulphate  of  soda.  The  sulphate  of  lime 
precipitates,  the  solution  being  crystallized,  and  the  crystals 
subsequently  purified  by  draining,  fusing,  solution,  and  re- 
crystallization. The  crystals  effloresce  in  the  air,  and  are 
soluble  in  water  and  alcohol. 

Acetate  of  Ammonia — Spirit  of  Minder er its. — The  so- 
lution is  made  by  saturating  acetic  acid  with  carbonate  of 
ammonia,  and  the  solid  by  distilling  acetate  of  lime  and  hy- 
drochlorate of  ammonia ; the  acetate  of  ammonia  passes 
over,  and  chloride  of  calcium  is  left. 

Acetate  of  Alumina  is  made  by  the  decomposition  of  a 
solution  of  alum  by  acetate  of  lead.  It  is  much  used  by 
dyers  as  a mordant. 

Acetates  of  Lead.  — 1st.  Neutral  Acetate  {Sugar  of 
Lead)  may  be  made  by  dissolving  litharge  in  acetic  acid. 
It  occurs  in  colorless  prismatic  crystals,  and  also  in  crystal- 
line masses.  It  has  a sweetish,  astringent  taste,  from  which 
its  commercial  name  is  derived.  It  is  soluble  in  about  its 
own  weight  of  cold  water.  The  crystals  effloresce  in  the 
air.  2d.  Subacetates  of  Lead — Sesquibasic  Acetate — is 
formed  by  partially  decomposing  the  neutral  acetate  by  heat. 
Its  solution  is  known  as  Goulard's  Water.  Two  other  sub- 
acetates may  be  made  by  the  action  of  ammonia  on  the  neu- 
tral salt.  Their  solutions  have  an  alkaline  reaction,  absorb 
carbonic  acid  from  the  air,  and  give  rise  to  a precipitate  of 
the  basic  carbonate. 

Acetates  of  Copper. — 1st.  Neutral  Acetate — Distilled 
Verdigris — made  by  dissolving  verdigris  in  hot  acetic  acid. 
On  cooling,  it  yields  green  crystals,  soluble  both  in  water 

Mention  some  of  the  more  important  salts  of  acetic  acid?  How  is  the 
ucetate  of  soda  made  ? What  is  the  spirit  of  Mindererus  ? For  what  pur- 
pose is  acetate  of  alumina  used  ? What  varieties  of  acetate  of  lead  are  there, 
illd  how  are  they  formed  ? What  are  the  varieties  of  acet.ite  of  copper  ? 


DERIVATIVES  OF  ACETYLE. 


341 


and  alcohol.  It  is  used  as  a paint.  2d.  Bibasic  Acetates 
of  Copper — Yerdigris — may  be  made  by  the  action  of  vin- 
egar and  air  conjointly  on  metallic  copper.  Verdigris  is  a 
mixture  of  several  acetates,  one  of  which  may  be  obtained 
by  digesting  it  in  warm  water ; a second  arises  on  boiling 
this  ; the  insoluble  residue  of  the  verdigris  contains  a third. 


LECTURE  LXXV. 

Derivatives  of  Acetyle. — The  Kakodyle  Group. — 
Clilor acetic  Acid. — Acetone. — Chloral  and  Heavy  Mu- 
riatic  Ether. — Substitutions  of  Chlorine  i?i  Eight  Mu- 
riatic Ether. — Sulphur-alcohol. — Its  Relations  to  Mer- 
cury.— Xanthic  Acid. — The  Kakodyle  Group. — Oxide. 
— Chloride. — Kakodijlic  Acid. 

Chloracetic  Acid  {C^HO^Cl^.  — This  remarkable 
body  is  formed  when  a small  quantity  of  crystallized  acetic 
acid  is  exposed  to  the  sunshine  in  a jar-full  of  chlorine  gas. 
The  crystals  which  form  on  the  inside  of  the  vessel  are  to 
be  dissolved  in  water,  and  the  solution  evaporated  in  vacuo 
with  capsules  containing  caustic  potash  and  oil  of  vitriol. 
A little  oxalic  acid  is  first  deposited,  and  then  the  chlora- 
cetic acid  crystallizes  as  a colorless  and  deliquescent  body, 
with  a powerfully  acid  taste,  and  capable  of  corroding  the 
skin.  It  melts  at  115^  F.,  and  boils  at  390°.  By  com- 
paring its  constitution  with  that  of  acetic  acid,  it  will  be 
seen  that  in  its  formation  three  atoms  of  chlorine  have  been 
substituted  for  three  of  hydrogen.  It  yields  an  extensive 
series  of  salts. 

Acetone — Pyroacetic  Spirit  {C^H^O) — may  be  made  by 
passing  acetic  acid  vapor  through  a red-hot  iron  tube,  or  by 
the  distillation  of  dry  acetate  of  lead.  It  is  a limpid,  color- 
less, and  volatile  liquid,  boiling  at  132°,  burns  with  a bright 
flame,  and  is  soluble  in  water  and  alcohol.  Nordhausen  oil 
of  vitriol,  distilled  with  acetone,  abstracts  from  it  one  atom 
)f  water,  yielding  an  oily  body,  the  constitution  of  which  is 
C^H^  ; it  is  lighter  than  water,  and  has  an  odor  of  garlic. 
Sir  R.  Kane  considers  acetone  to  be  the  hydrated  oxide 


How  is  chloracetic  acid  made  ? What  is  the  relationship  between  acetic 
and  chloracet  ic  acid  ? What  is  the  mode  of  preparing  pyroacetic  spirit  ? 


342 


CHLORAL, 


of  an  ideal  radical,  Mesityle,  and  has  been  able  to 

produce  the  oxide  and  chloride  ofmesityle.  Zeise  also  dis- 
covered a compound  consisting  of  the  oxide  of  mesityle  and 
bichloride  of  platinum. 

Chloral  {C — When  dry  chlorine  is  passed 
into  anhydrous  alcohol,  and  the  action  finished  by  the  aid 
of  heat,  hydrochloric  acid  is  produced  ; and  on  its  ceasing 
to  appear,  if  the  product  be  agitated  with  three  times  its 
volume  of  oil  of  vitriol,  and  the  mixture  warmed,  an  oily 
liquid  floats  on  the  acid  : this  is  chloral.  It  may  be  puri- 
fied by  successive  distillation  from  oil  of  vitriol  and  quick- 
lime. It  is  an  oily,  colorless  liquid,  which  causes  a flow  of 
tears,  leaves  a transient  greasy  stain  upon  paper,  has  a den- 
sity of  1*502,  boils  at  201°,  is  soluble  in  water  and  alcohol ; 
it  yields  no  precipitate  with  nitrate  of  silver.  When  kept 
for  a length  of  time  in  a sealed  tube,  it  spontaneously  be- 
comes a white,  solid,  insoluble  chloral.  In  this  condition  it 
is  little  soluble  in  water,  and  reverts  to  its  other  state  by 
being  warmed. 

If  chlorine  acts  on  alcohol  containing  water,  heavy  Mu~ 
riatic  Ether  is  formed.  It  is  a colorless  and  volatile  liquid. 

The  action  of  chlorine  upon  common  ether,  and  also  on 
the  compound  ethers,  is  very  interesting.  It  consists  in  the 
gradual  removal  of  hydrogen,  chlorine  being  substituted  for 
it.  This,  in  many  instances  in  which  the  aid  of  the  sun- 
light is  resorted  to,  terminates  in  the  entire  removal  of  the 
hydrogen.  In  the  compound  ethers  it  is  the  basic  hydrogen 
which  is  removed,  while  that  of  the  acid  escapes,  as  in  the 
case  of  chlorureted  acetic  and  chlorureted  formic  ethers. 
When  the  vapor  of  light  hydrochloric  ether  is  acted  upon 
by  chlorine  gas,  a complete  series  of  compounds  may  be  ob- 
tained, the  hydrogen  eventually  disappearing  : 

Hydrochloric  ether C^H^Cl ; 

Monochlorureted  hydrochloric  ether  . . ; 

Bichlorureted  “ “ . . 

TricHorureted  “ “ . . C^lf^Cl^; 

Quadrichlorureted  ‘‘  “ . . C^H  Cl^; 

Perchloride  of  carbon CIq  ; 

furnishing,  therefore,  a very  striking  instance  of  the  doctrine 
of  substitution. 

Mercaptan — Sulphii7''alcohol{^C — is  prepared  by 
saturating  a solution  of  caustic  potash,  specific  gravity  1*3, 

What  is  mesityle  ? What  is  chloral  ? Under  what  circumstances  does 
insoluble  chloral  form  ? Describe  the  successive  action  of  chlorine  upon 
ether.  How  is  mercaptan  prepared  ? 


XANTHIC  ACID. KAKODYLE, 


343 


with  sulphureted  hydrogen,  and  distilling  it  with  an  equa. 
volume  of  sulphovinate  of  lime  of  the  same  density.  It 
passes  over  with  water,  on  the  surface  of  which  it  floats  as 
a colorless  liquid,  specific  gravity  *842,  soluble  in  alcohol. 
It  boils  at  97°,  smells  like  onions,  and  burns  with  a blue 
flame.  Mercaptan  corresponds  to  alcohol  in  which  all  the 
oxygen  has  been  replaced  by  sulphur ; but  in  its  action  on 
metallic  oxides  it  answers  to  the  hydruret  of  a compound  rad- 
ical, Thus,  with  peroxide  of  mercury,  it  forms  a 

mercaptide  with  the  production  of  water ; and  this  may  be 
decomposed  by  sulphureted  hydrogen,  sulphuret  of  mercury 
subsiding,  and  mercaptan  being  reproduced.  Mercaptan 
derives  its  name  from  its  strong  affinity  for  mercury  [Mer- 
curium  C'aptans). 

Xanthic  Acid  {CqH^S^O-{-HO). — Hydrate  of  potash  is 
to  be  dissolved  in  twelve  parts  of  alcohol,  specific  gravity 
*800,  and  bisulphuret  of  carbon  dropped  into  the  solution 
until  it  ceases  to  have  an  alkaline  reaction.  On  cooling  to 
zero,  the  xanthate  of  potash  crystallizes:  it  is  to  be  dried 
in  vacuo.  It  is  soluble  in  water  and  alcohol,  but  not  in 
ether  ; and  from  it  xanthic  acid  may  be  procured  by  the  ac- 
tion of  dilute  hydrochloric  acid.  Xanthic  acid  is  an  oily 
liquid,  heavier  than  water,  which  first  reddens  and  then 
bleaches  litmus  paper.  At  75°  it  is  decomposed  into  alco- 
hol and  bisulphuret  of  carbon.  It  is  also  decomposed  by  the 
action  of  the  air. 

Kakodyle  {C^HqAs  =z  Kd)  is  a compound  radical,  which 
gives  rise  to  an  extensive  group  of  bodies,  in  which  it  acts 
the  part  of  a metal. 

The  Kakodyle  Group. 


Kakodyle,  C^H^As Kd. 

Oxide  of  kakodyle  = KdO. 

Chloride  “ = KdCl. 

Iodide  “ = Kdl. 

Sulphuret  = KdS. 

&c.  &c. 


Kakodyle  may  be  obtained  by  decomposing  the  chloride 
of  kakodyle  with  metallic  zinc  in  an  apparatus  filled  with 
carbonic  acid  gas,  and  may  be  purified  by  redistillation  from 
zinc,  similar  precautions  being  taken  to  exclude  atmospheric 
air.  It  is  a colorless  liquid,  of  a powerful  odor,  taking  fire 

What  remarkable  qualities  does  mercaptan  possess  ? From  what  is  its 
name  derived?  What  is  the  process  for  preparing  xanthic  acid?  What  is 
ks  action  on  litmus  paper  ? What  is  kakodyle  ? How  may  it  be  isolated  . 


344 


KAKODYLE. 


on  the  contact  of  air,  oxygen  gas,  or  chlorine ; boils  at  338°, 
crystallizes  at  21°,  and  is  decomposed  by  a red  heat  into 
olefiant  gas,  light  carbureted  hydrogen,  and  arsenic. 

Oxide  of  Kahodyle — Alkarsine — Cadeds  Fuming  Liq~ 
uor — is  prepared  by  the  distillation  of  acetate  of  potash  and 
arsenious  acid,  receiving  the  products  in  an  ice-cold  vessel, 
the  temperature  being  finally  carried  to  a red  heat.  The 
oxide  comes  over  in  an  impure  state,  sinking  to  the  bottom 
of  the  other  products.  It  is  t6  be  decanted,  washed  with 
water,  boiled,  and  then  distilled  in  a vesseLfull  of  hydrogen 
from  hydrate  of  potash.  It  is  a colorless  liquid,  specific 
gravity  1*462,  boils  at  300°,  and  solidifies  at  9°;  is  spar- 
ingly soluble  in  water,  but  more  so  in  alcohol ; is  excessive- 
ly poisonous,  possessing  a concentrated  smell  like  garlic. 
Heated  in  the  air,  it  burns,  producing  carbonic  acid,  water, 
and  arsenious  acid. 

Chloride  of  Kakodyle  may  be  procured  by  the  action  of 
a dilute  solution  of  corrosive  sublimate  on  a dilute  alcoholic 
solution  of  oxide  of  kakodyle ; a white  precipitate  falls, 
which,  distilled  with  strong  hydrochloric  acid,  yields  cor- 
rosive sublimate,  water,  and  the  chloride  of  kakodyle  passes 
over.  When  purified  by  chloride  of  calcium,  and  distilled 
in  an  atmosphere  of  carbonic  acid,  it  is  a colorless  liquid,  of 
a dreadful  odor,  heavier  than  water,  and  insoluble  therein, 
but  soluble  in  alcohol.  It  is  very  poisonous.  It  boils  at 
about  212°,  the  vapor  taking  fire  in  the  air. 

Kakodylic  Acid — Alcargen  {Kd . O3) — may  be  made  by 
the  action  of  oxide  of  mercury  upon  oxide  of  kakodyle  un- 
der the  surface  of  water,  at  a low  temperature.  Kakodylic 
acid  forms  crystals  which  deliquesce  in  the  air,  are  soluble 
in  water  and  alcohol,  but  not  in  ether.  It  is  not  acted  Upon 
by  oxydizing  agents,  such  as  nitric  acid,  but  is  reduced  to 
oxide  of  kakodyle  by  several  deoxydizing  bodies.  It  is  not' 
poisonous. 

Kakodyle  furnishes  a complete  series  of  bodies  : the  iodide, 
sulphuret,  cyanide,  and  a substance  isomeric  with  the  oxide, 
which  has  the  name  of  parakakodylic  oxide. 

What  are  alkarsine  and  Cadet’s  fuming  liquor  ? How  is  it  prepared,  and 
what  are  its  properties  ? What  is  the  process  for  preparing  the  chloride  of 
kakodyle  ? What  are  its  properties  ? What  is  the  constitution  of  alcargen  ? 


COMPOUNDS  OP  METHYLE. 


345 


LECTURE  LXXVI. 

The  Wood-Spirit  Group. — Methyle. — Its  Oxide  and  Hy 
drated  Oxide. — Salts  of  Methyle. — Formic  Acid,  nat 
ural  and  artificial  Production  of. — Derivatives  of  Wooa 
Spirit. — Substitutions  of  Chlorine  in  Oxide  of  Methyle. 
— Substitutions  in  Chloride  of  Methyle. 

In  the  destructive  distillation  of  wood  in  the  preparation 
of  pyroligneous  acid,  there  passes  over  a body  to  which  the 
name  of  wood  spirit  has  been  given.  This  is  the  hydrated 
oxide,  or  alcohol  of  an  ideal  compound  radical,  passing  un- 
der the  name  of  methyle. 

The  Methyle  Group. 

Methyle,  = Me. 

Oxide  of  methyle  . . . . = MeO. 

Hydrated  oxide = MeO  HO. 

Chloride = MeCl. 

&c.  &c. 

Oxide  of  Methyle — Methylic  Ether — Wood  Ether  {C^ 
H^O). — This  substance  is  made  from  the  hydrated  oxide 
on  the  same  principle  that  ether  is  obtained  from  alcohol  : 
one  part  of  wood  spirit  and  four  of  oil  of  vitriol  being  heat- 
ed in  a flask,  the  vapor  is  passed  through  a small  quantity 
of  caustic  potash  solution,  and  received  at  the  mercurial 
trough.  It  is  a permanently  elastic  gas,  colorless,  and  has 
a specific  gravity  of  1*617,  burns  with  a pale  flame,  is  very 
soluble  in  water,  which  takes  up  thirty-three  times  its  vol- 
ume of  it,  and  yields  it  unchanged  when  heated. 

Hydrated  Oxide  of  Methyle — Wood  Spirit — Pyroxijlic 
Spirit — may  be  separated  from  crude  wood  vinegar  hy  dis- 
tillation. It  passes  over  with  the  first  portions  along  with 
a little  acid,  which,  being  neutralized  with  hydrate  of  lime, 
the  wood  spirit  may  he  separated  from  the  oil  which  floats 
on  its  surface,  and  redistilled.  The  product  thus  obtained 
may  he  rectified  in  the  same  manner  as  common  alcohol, 
and  rendered  anhydrous  hy  quicklime.  It  is  then  a color- 
less liquid,  of  a hot  taste  and  peculiar  smell.  It  boils  at 

Under  what  circumstances  is  wood  spirit  produced  ? What  is  its  ideal 
compound  radical?  How  is  the  oxide  of  methyle  prepared,  and  what  is  its 
form  ? What  is  the  constitution  of  pyroxylic  spirit  ? What  are  its  proper- 
ties ? 


346 


COMPOUNDS  OP  METHYLS. 


152°,  and  has  a specific  gravity  of  *798  at  68°.  It  is  sol- 
uble in  water,  dissolves  resins  and  oils,  and  may  be  burned 
like  spirit  of  wine.  It  then  exhales  a peculiar  odor. 

Chloride  of  Methyle  [MeCl)  may  be  made  from  the  re- 
action of  sulphuric  acid  upon  common  salt  and  wood  spirit. 
It  is  a colorless  gas,  which  may  be  collected  over  water ; 
has  a density  of  1*731.  It  has  a peculiar  odor,  is  inflam- 
mable, and  may  be  decomposed  by  passing  through  a red- 
hot  tube. 

Sul'phate  of  Oxide  of  Methyle  {MeO,  SO^)  may  be  pre- 
pared by  distilling  one  part  of  wood  spirit  with  eight  or  ten 
of  oil  of  vitriol  ; the  product  is  to  be  washed  with  water, 
and  redistilled  from  caustic  baryta.  It  is  an  oily,  neutral 
liquid,  smelling  like  garlic ; specific  gravity  1*324.  It  boils 
at  370°.  It  is  not  soluble  in  water,  but  is  decomposed  by 
that  liquid,  especially  at  the  boiling  temperature,  into  sul- 
phomet hylic  acid  and  hydrated  oxide  of  methyle.  It  is  to 
be  observed,  that  in  the  series  of  wine  alcohol  there  is  no 
compound  corresponding  to  this. 

Nitrate  of  Oxide  of  Methyle  [MeO,  NO^)  is  obtained 
by  the  action  of  a mixture  of  wood  spirit  and  oil  of  vitriol 
upon  nitrate  of  potash.  It  is  a colorless  liquid,  heavier  than 
water  ; boils  at  150°  ; burns  with  a yellow  flame.  Its  va- 
por explodes  when  heated.  In  a solution  of  caustic  potash, 
it  decomposes  into  nitrate  of  potash  and  wood  spirit. 

Oxalate  of  Oxide  of  Methyle  {MeO,  C^O^  is  made  by 
distilling  oxalic  acid,  wood  spirit,  and  oil  of  vitriol.  The 
liquid  which  is  collected  is  allowed  to  evaporate  ; it  yields 
crystals  of  the  oxalate.  When  pure,  it  is  colorless  ; melts 
at  124°,  and  boils  at  322°.  It  is  decomposed  by  hot  water 
into  oxalic  acid  and  wood  spirit,  by  solution  of  ammonia 
into  oxamide  and  wood  spirit. 

Sulphomethylic  Acid  {MeO,  2SO^  + HO),  the  com- 
pound corresponding  to  sulphovinic  acid,  and  prepared  in 
the  same  way,  by  substituting  wood  spirit  for  alcohol.  It 
is  thus  procured  as  a sirup  or  in  small  crystals,  soluble  in 
water  and  alcohol.  It  is  an  instable  body,  and  possesses 
many  analogies  with  sulphovinic  acid. 

Formic  Acid{C2HO^  + HO). — This  acid,  in  the  wood- 

For  what  purposes  may  pyroxylic  spirit  be  used  ? ‘ How  is  the  chloride 
of  methyle  prepared?  In  the  wine  series,  is  there  any  compound  analogous 
to  sulphate  of  oxide  of  methyle  ? How  is  the  nitrate  obtained,  and  what 
are  its  properties  ? Describe  the  preparation  of  the  oxalate  and  of  sulpho 
methylic  acid.  What  is  the  constitution  of  formic  acid  ? 


FORMIC  ACID. — CHLOROFORM. 


347 


spirit  series,  is  the  analogue  of  acetic  acid  in  the  alcohol  se 
ries.  It  may  be  procured  on  principles  similar  to  those  in- 
volved in  the  preparation  of  acetic  acid,  as  by  the  gradual 
oxydation  of  the  vapor  of  wood  spirit  in  the  air  under  the 
influence  of  black  platinum.  In  a dilute  state  it  may  be 
prepared  by  distilling  one  part  of  sugar,  three  of  peroxide 
of  manganese,  and  two  of  water,  with  three  parts  of  sul- 
phuric acid,  diluted  with  an  equal  weight  of  water.  The 
liquid  which  distills  is  to  be  neutralized  by  carbonate  of 
soda,  purified  by  animal  charcoal,  and  redistilled  along  with 
sulphuric  acid.  It  occurs  naturally  in  the  bodies  of  red  ants, 
and  hence  has  obtained  the  name  of  formic  acid.  From 
the  distillation  of  those  animals  it  was  originally  procured. 

Anhydrous  formic  acid  obviously  contains  the 

elements  of  two  atoms  of  carbonic  oxide  and  one  of  water. 
It  yields  two  hydrates,  respectively  containing  one  and  two 
atoms  of  water.  The  first,  for  which  the  formula  has  al- 
ready been  given,  is  procured  by  the  action  of  sulphureted 
hydrogen  on  formiate  of  lead.  It  is  a colorless  liquid,  of  a 
strong  odor  ; boils  at  212°,  and  crystallizes  below  32°.  It  is 
inflammable,  and  has  a specific  gravity  of  1’235.  It  blis- 
ters the  skin.  Formic  acid  yields  a complete  series  of  salts. 

Chloroform  {C^HCl^)  is  made  by  distilling  wood  spirit 
with  a solution  of  chloride  of  lime.  It  is  a colorless  liquid , 
specific  gravity  1*48  ; boils  at  141°.  It  burns  with  a green 
flame,  and  is  decomposed  by  an  alcoholic  solution  of  potash 
into  chloride  of  potassium  and  formiate  of  potash.  The  re- 
lationship between  formic  acid  and  chloroform  is  obvious  : 
it  consists  in  the  substitution  of  three  atoms  of  chlorine  for 
three  of  oxygen.'  There  are  also  two  analogous  compounds: 


Formomethylal  is  prepared  by  distilling  wood 

spirit,  oxide  of  manganese,  and  dilute  sulphuric  acid.  On 
saturating  the  product  with  potash,  formomethylal  separates 
as  a colorless  oily  liquid:  specific  gravity  *855;  boils  at 
107°,  and  soluble  in  water. 

Methyle-mercajptan. — Formed  as  the  common  mercap- 
tan, by  substituting  sulphomethylate  of  potash  for  sulphovi- 
nate  of  lime.  It  is  analogous  to  common  mercaptan. 

How  is  it  procured?  From  what  circumstance  is  its  name  deprived? 
What  are  its  properties  ? How  is  chloroform  obtained  ? What  is  the  pro- 


Bromoform  . . 

Iodoform  . . . 


cpss  for  preparing  formomethylal  ? 


348 


THE  POTATO-OIL  GROUP. 


When  chlorine  is  made  to  act  on  the  oxide  of  methyle 
at  common  temperatures,  it  removes  one  of  the  hydrogen 
atoms ; and  by  continuing  the  action,  a second  may  be  taken 
away,  and  the  process  of  substitution,  as  shown  in  the  fol- 
lowing series,  may  be  carried  so  far  as  to  end  in  the  removal 
of  oxygen  and  the  production  of  chloride  of  carbon. 


Oxide  of  methyle C^H^O. 

1st  substitution Cl. 

2d  “ C^H  O,  C/g. 

3d  “ O,  Cl^. 

4th  “ (chloride  of  carbon)  . Cl^. 

Other  methylic  compounds  furnish  similar  series,  thus  : 


Chloride  of  methyle 


1st  substitution 

2d  “ (chloroform) Cl^. 

3d  “ (chloride  of  carbon)  . . Cl^. 


LECTURE  LXXYIL 

The  Potato-Oil  Group. — Fusel  Oil. — Chloride  of  Amyle. 
—Sidphmnylic  Acid. — Amilen. — Relations  of  Yaleria- 
nic  Acid. 

The  Benzyle  Group.- — Oil  of  Bitter  Almonds. — Benzoic 
Acid. — ^id])hohenzoic  Acid. — Chloride  of  Benzyle. — 
Benzamide. 

In  the  distillation  of  brandy  from  potatoes,  a volatile  oil 
passes  over.  It  is  regarded  as  the  hydrated  oxide  of  an 
ideal  compound  radical,  which  passes  under  the  name  of 
Amyle,  having  the  constitution 

The  Potato-Oil  Group. 

Amyle,  Cio^^n —Ayl. 

Amyle  ether =AylO. 

Amyle  alcohol  (potato  oil) AylO-\-HO. 

Chloride  of  amyle  . AylCl. 

&c.  &c. 

Amilen CiqHio. 

Valerianic  acid 

Of  these,  amyle  and  its  oxide,  amyle-ether,  are  ideal. 

Hydrated  Oxide  of  Amyle — Amyle  Alcohol — Potato  Oil 
— Fusel  Oil  {C ^qH^^O  + HO) . — This  substance  passes 

Describe  the  series  of  substitutions  of  chlorine  on  the  oxide  of  methyle. 
Describe  the  analogous  substitutions  with  chloride  of  methyle  ? What  is 
»,he  imaginary  radical  of  the  potato-oil  group?  What  are  the  nature  and  re- 
lations of  fusel  oil  ? 


COMPOUNDS  OF  AMYLE. 


349 


over  toward  the  end  of  the  first  distillation  of  potato  spirit, 
and  communicates  to  it  a milky  aspect.  'On  standing,  it  floats 
on  the  surface,  and  may  be  purified  by  washing  with  water, 
drying  with  chloride  of  calcium,  and  redistillation.  It  is  a 
fluid  oil  of  a suffocating  odor,  which  acts  powerfully  on  the 
animal  system.  Its  specific  gravity  is  *818  ; it  boils  at  269'^. 

Chloride  of  Amyle  {AylCl)  is  made  by  distilling  equal 
weights  of  potato  oil  and  perchloride  of  phosphorus,  w^ash- 
ing  with  potash  water,  and  redistilling  from  chloride  of  cal- 
cium. It  as  an  aromatic  liquid,  boils  at  215°,  and  burns 
with  a green  flame.  Under  the  influence  of  sunshine,  eight 
of  its  hydrogen  atoms  may  be  removed,  eight  chlorine  atoms 
being  substituted  for  them,  yielding 

forming  chlorureted  chloride  of  amyle. 

The  Iodide  and  Bromide  of  Amyle  are  compounds  anal- 
ogous to  the  chloride. 

Acetate  of  Oxide  of  Amyle  is  obtained  by  distilling  ace- 
tate of  potash,  potato  oil,  and  sulphuric  acid.  It  is  a color- 
less liquid,  which  boils  at  257°. 

Sulphamilic  Acid  {AylO,  2SO^H+ O)  is  generated 
when  sulphuric  acid  is  made  to  act  on  an  equal  weight  of 
potato  oil.  From  this,  by  the  successive  action  of  carbonate 
of  baryta  and  sulphuric  acid,  it  may  be  procured  by  oper- 
ating on  the  same  principles  as  for  sulphovinic  acid,  to  which, 
both  in  constitution  and  properties,  it  is  the  analogue.  It 
is  a sirupy  or  crystalline  body,  and  is  decomposed  by  ebul- 
lition into  potato  oil  and  sulphuric  acid. 

Amilen  is  obtained  by  the  action  of  anhydrous 

phosphoric  acid  on  potato  oil  \ it  is  an  oily  liquid,  which  boils 
at  320°.  In  constitution  and  position,  it  therefore  occupies, 
in  the  amyle  series,  the  same  situation  that  olefiant  gas 
does  for  the  wine-alcohol  series,  and,  indeed,  is  isomeric 
with  that  body. 

Valerianic  Acid  bears  the  same  relation  to 

the  amyle  group  which  acetic  acid  does  to  the  wine-alcohol 
group,  or  formic  acid  to  the  wood-spirit  group.  It  is  form- 
ed when  warm  potato  oil  is  dropped  on  platinum  black  in 
contact  with  the  air.  It  occurs  naturally  in  the  root  of  the 
Valeriana  OJ)icinalis,  but  is  best  made  by  heating  potato 


What  are  the  properties  of  the  chloride  of  amyle?  To  what  substance  is 
sulphamilic  acid  analogous?  What  relation  is  there  between  amilen  and 
olefiant  gas  ? What  is  the  relation  between  acetic  and  valerianic  acids  ? 
From  what  natural  source  may  the  latter  be  derived  ? 


350 


THE  BENZYLE  GROUP. 


oil  in  a flask,  with  a mixture  of  quicklime  and  hydrate  of 
potash,  for  several  hours  at  a temperature  of  400°.  The 
white  residue  is  immersed  in  cold  water,  and  distilled  with 
a slight  excess  of  sulphuric  acid,  so  as  to  drive  off  hydrated 
valerianic  acid  and  water.  It  is  a colorless  oil  of  an  acid 
taste,  combustible,  and  boiling  at  347°.  When  acted, upon 
by  chlorine  in  the  dark,  and  the  action  aided  by  heat,  it 
gives  rise  to  Chlorovalerisic  Acid  + HO),  in 

which  there  has  been  a removal  of  three  hydrogen  atoms 
and  a substitution  of  three  of  chlorine.  Under  the  influence 
of  the  sunshine,  by  the  same  process,  another  hydrogen  atom 
is  removed,  and  Chlorovalerosic  Acid  forms,  its  constitution 
being  C^qH^CI^O^  + HO. 


Of  this  series,  benzyle,  the  radical,  is  an  ideal  body.  It  is 
a radical  which  discharges  the  functions  of  a metallic  body, 
giving  rise  to  oxides,  chlorides,  iodides,  &c.,  as  the  table 
shows. 

Hydruret  of  Benzyle — Oil  of  Bitter  Almonds  {BzH) 
— is  obtained  by  the  distillation  of  bitter  almonds,  from  which 
the  fixed  oil  has  been  expressed,  with  water,  and  arises  from 
the  action  of  the  water  upon  Amygdaline  contained  in  the 
seed.  It  may  be  purified  by  distillation  from  protochloride 
of  iron  with  hydrate  of  lime  in  excess,  and  is  a colorless 
liquid  of  an  agreeable  odor,  slightly  heavier  than  water,  and 
also  slightly  soluble  therein,  but  very  soluble  in  alcohol  and 
ether.  It  boils  at  356°.  In  the  air  it  passes  into  benzoic 
acid  by  absorbing  oxygen. 

Oxide  of  Benzyle — Benzoic  Acid  {BzO  + HO.) — This 
acid  is  obtained  by  sublimation  from  gum  benzoin,  that  sub- 
stance being  placed  in  a shallow  vessel,  over  the  top  of 
which  a cover  of  filtering  paper  is  pasted,  and  this  covered 
by  a taller  cylinder  of  stouter  paper.  On  heating,  the  va- 
pors pass  through  the  filtering  paper,  and,  condensing  in 
feathery  crystals  in  the  space  above,  fall  down  upon  the  pa- 

How  is  valerianic  acid  made  artificially  ? What  is  the  successive  action 
of  chlorine  upon  it  ? What  is  the  radical  of  the  benzyle  series  ? What  is 
oil  of  bitter  almonds?  From  what  substance  does  it  arise?  What  is  ben 
zoic  acid?  By  what  nrocc'^scs  ma3’  it  be  prepared^ 


The  Benzyle  Group. 


Benzyle,  6^14-^5^2 

Hydruret  of  benzyle 

Oxide  of  benzyle  (benzoic  acid)  . . 

Chloride  


=zBz. 


&c. 


DERIVATIVES  OF  6ENZYLE. 


351 


per  and  are  retained  by  it.  A better  method  is  to  boil  a 
fixture  of  the  gum  with  hydrate  of  hme,  ^ 

the  solution,  add  hydrochloric  acid,  and  the  benzoic  acid 
crystallizes  in  thin  plates  on  cooling.  It  may  be  subse- 
quently sublimed.  When  pure  it  has  no  odor.  It  melts  at 
212°,  and  boils  at  462°.  Its  vapor  excites  coughing  it 
is  much  more  soluble  in  hot  than  m cold  water.  It  terms 
a series  of  salts,  and  is  sometimes  used  for  the  separation  ot 
iron  from  other  metals.  ti-^\ 

Sulphobenzoic  Add  SO^  4-  2ff  ),  a i 

acid,  formed  by  the  action  of  anhydrous  sulphuric  acid  upon 
benzoic  acid,  the  mass  being  dissolved  in  water  and  neu- 
tralized by  carbonate  of  baryta.  On  filtering,  and  adding 
hydrochloric  acid  to  the  hot  solution,  on  cooling  the  sulpho- 
bLzoate  of  baryta  crystallizes,  which  may  be  decomposed 
by  dilute  sulphuric  acid.  It  is  a white  crystalline  mass. 

Chlorideof  Benzyle  (.BzCZ).— When  chlorine  gas  is  pass- 
ed through  oil  of  bitter  almonds,  hydrochloric  acid  is  formed, 
and,  after  expelling  the  excess  of  chlorine  by  heat,  chloride 
of  benzyle  remains.  It  is  a colorless  liquid,  of  a disagree- 
able odor,  heavier  than  water,  combustible,  and  decomposed 
bv  boiling  water  into  benzoic  and  hydrochloric  acids. 

Benzamide  {C,,H,NO^)  is  foimed  by  the  action  of  chlo- 
ride of  benzyle  on  dry  ammonia,  the  hydrochlorate  ot  atn 
monia  being  removed  from  the  resulting  white  mass  by  cold 
water  From  a solution  in  boiling  water,  the  benzamide 
crystallizes.  It  melts  at  239°.  It  corresponds  in  its  chem- 
ical relations  to  oxamide.  , , „ 

Hydrobenzamide  made  by  e ac  lo 

pure  oil  of  bitter  almonds  on  solution  of  ammonia,  the  pro- 
duct being  washed  with  ether,  and  from  its  alcoholic  solu- 
tion this  substance  crystallizes  ; but  when  impure  almond 
oil  is  employed,  three  other  compounds  may  be  obtained  . 
they  are  benzhydramide,  azobenzoyle,  and  nitrobenzoyle. 

■ What  is  the  process  for  preparing  ^“fohobenzoic  acid?  ^ 

ride  of  benzyle  made  ? How  are  benzamide  and  hydrobenzamide  lormea  . 


352 


DERIVATIVES  OF  BENZYLE. 


LECTURE  LXXVIII. 

The  Salicyle  and  Cinnamyle  Groups. — ^enzoine^  Sen- 
zone,  Benzine.  — Hippuric  Acid.  — The  Salicyle 
Group. — Artificial  Formation  of  Oil  of  Spircea,— 
Compounds  of  Salicyle. — Melanie  Acid. — The  Cinna- 
myle Group. — Compounds  of  Cinnamyle. 

Benzoine  a body  isomeric  with  bitter  al- 

mond oil.  It  is  tbund  in  the  residue  after  purifying  that 
oil  from  hydrocyanic  acid  by  distillation  from  lime  and  ox- 
ide  of  iron,  and  may  be  obtained  by  dissolving-  out  those 
bodies  by  hydrochloric  acid.  It  crystallizes  from  an  alco- 
holic solution,  on  cooling,  in  colorless  crystals,  which  melt 
at  248°.  It  dissolves  in  an  alcoholic  solution  of  caustic 
potash,  which,  by  boiling  until  the  violet  color  has  disap- 
peped,  furnishes  benzilate  of  potash,  a salt  from  which  ben- 
zihc  acid  may  be  obtained  by  hydrochloric  acid.  The  con- 
stitution of  Benzilic  Acid  is  -f  HO, 

Benzone  {C ^^H^O)  is  obtained  by  the  distillation  of  dry 
benzoate  of  lirne  at  a high  temperature,  carbonate  of  lime 
remaining  behind.  The  decomposition  is  interesting,  the 
benzoic  acid  atom  being  divided,  and  yielding  benzone  and 
carbonic  acid. 

C,,H,0,  C,,H,0  + CO,. 

Benzine  ( C^giTg)  arises  when  crystallized  benzoic  acid 
IS  distilled  from  hydrate  of  lime  at  a red  heat.  It  is  an 
oily  liquid,  and,  after  being  separated  from  the  water  which 
cornes  over  with  it,  is  to  be  rectified.  It  boils  at  187°,  so- 
lidifies  at  32°,  and  is  lighter  than  water.  In  its  formation 
tie  liydiated  benzoic  acid  is  resolved  into  benzine  and  car- 
bonic acid. 

C^^H^  + 2(CO,). 

Sulpliohe7tzide{C^^H,SO^)  is  formed  by  taking  the  sub- 
stance which  arises  from  the  union  of  benzine  with  anhy- 
drous  sulphuric  acid,  and  acting  upon  it  with  an  excess  of 


benzoine  bear  to  oil  of  bitter  almonds  ? What  is  the 
■ distillation  of  dry  benzoate  of  lime  ? What  is  the  nature  of 

;he  decomposition?  What  is  the  result  of  the  distillation  of  crystallized 
lenzoic  acid  and  hydrate  of  lime  ? What  is  the  result  of  the  actfon  of  an- 
ydrous  sulphuric  acid  and  benzine  ? 


Tiin  SAI.ICYLE  GROUP. 


353 


water.  The  sulphohenzide,  which  is  insoluble  in  that  liq 
uid,  may  be  obtained  in  crystals  from  its  ethereal  solution. 
It  melts  at  212°  F.  From  the  acid  liquid  from  which  it 
has  been  separated  hyposulphobenzic  acid  may  be  obtained. 
Its  constitution  is 

Nitrobenzide  produced  by  the  action  of 

fuming  nitric  acid  on  benzine,  with  the  aid  of  heat.  It  is 
an  oily  liquid,  of  a sweet  taste,  heavier  than  water,  and 
boiling  at  415°.  From  it  Azohenzide  may  be 

obtained  by  distillation  with  an  alcoholic  solution  of  caus- 
tic potash,  in  the  form  of  red  crystals. 

Chlorhenzinei^CYiddi^Cl^  is  formed  by  the  union  of  ben- 
zine and  chlorine  in  the  sun-rays.  When  distilled,  the  solid 
yields  hydrochloric  acid  and  a liquid,  Chlorbenzide 

Hippuric  Acid  ( C^qH^NO^  + HO)  is  found  in  the  urine 
of  graminivorous  animals,  and  occurs  in  the  urine  of  per- 
sons who  have  taken  benzoic  acid.  It  may  be  prepared  by 
evaporating  the  fresh  urine  of  the  cow,  and  acidulating  the 
concentrated  liquor  with  hydrochloric  acid  ; crystals  of 
hippuric  acid  are  deposited,  which  may  be  decolorized  by 
bleaching  liquor  and  hydrochloric  acid.  It  crystallizes  in 
square  prisms,  sparingly  soluble  in  cold  water,  of  a bitter 
taste  and  acid  reaction.  By  a high  temperature  or  the  ac- 
tion of  sulphuric  acid,  it  yields  benzoic  acid. 

THE  SALICYLE  GROUP. 

There  is  contained  in  the  bark  of  the  willow  and  other 
trees  a bitter  crystalline  principle,  Salicine 
This  substance  may  be  extracted  by  boiling  the  bitter  bark 
in  water,  and  digesting  the  concentrated  solution  with  ox- 
ide of  lead  to  decolorize  it,  removing  any  dissolved  lead  by 
sulphureted  hydrogen,  and  evaporating  until  the  salicine 
crystallizes.  It  forms  white  needles  of  a bitter  taste,  much 
more  soluble  in  hot  than  cold  water.  Distilled  with  bi- 
chromate of  potash  and  sulphuric  acid,  it  yields  hydrosali- 
cylic  acid,  or  the  artificial  oil  of  meadow  sweet,  a substance 
containing  Salicyle^  the  ideal  compound  radical  of  a series 
of  bodies. 

What  is  the  action  of  nitric  acid  on  benzine  ? What  substance  results 
from  the  union  of  benzine  and  chlorine  ? From  what  sources  may  hippu 
ric  acid  be  obtained  ? Under  what  circumstances  does  benzoic  acid  pro- 
duce it?  From  what  is  salicine  obtained?  What  is  the  constitution  ot 
salicyle?  How  may  the  oil  of  meadow  sweet  be  made  artificially? 


354 


COMPOUNDS  OP  SALICYLD^ 


The  Salicyle  Group. 

Salicyle  si 

Hydrosalicylic  acid SIH. 

Iodide  of  salicyle = SlI.' 

Chloride ~ siCl. 

Hydrosalicylic  Acid— Oil  of  Sjdrcea  Ulmaria,  or  Mead- 
010  Sweet  H) — is  prepared  by  distilling  one 

part  of  salicine,  one  of  bichromate  of  pot  ash,  two  and  a half 
of  sulphuric  acid,  and  twenty  of  water ; the  salicine  being 
dissolved  in  one  portion  of  the  water,  and  the  acid  mixed 
with  the  rest.  The  yellow  oil  which  comes  over  is  rectified 
from  chloride  of  calcium.  It  may  also  be  obtained  by  distill- 
ing the  flowers  of  meadow  sweet  with  water.  It  is  trans- 
parent, but  turns  red  in  the  air.  It  is  slightly  soluble  in 
water,  and  very  soluble  in  alcohol.  Its  specific  gravity  is 
1 173 , it  boils  at  385*^  F.  It  contains  the  same  elements 
as  benzoic  acid. 

Salicylic  Acid  ^ + O)  is  obtained  by  the  action 

of  hydrate  of  potash  on  the  foregoing  body  by  the  assistance 
of  heat.  After  the  disengagement  of  hydrogen  is  over,  the 
mass  is  dissolved  in  water,  and  salicylic  acid  separates  in 
crystals  on  the  addition  of  hydrochloric  acid.  It  is  more 
soluble  in  hot  than  cold  water,  and  is  charred  by  hot  oil  of 
vitriol. 

Chloride  of  Salicyle  {C^^H^O^Cl)  is  made  by  the  action 
of  chlorine  on  hydrosalicylic  acid.  Its  crystals  are  insol- 
uble in  water,  but  soluble  in  solutions  of  fixed  alkalies,  from 
which  it  separates  on  the  addition  of  an  acid,  resisting  de- 
composition even  when  boiled  in  caustic  potash.  It  unites 
with  caustic  potash. 

bromide  and  Iodide  of  Salicyle  also  exist,  but  are  not 
of  interest. 

CJdorommide  — Ammoniacal  gas  is 

absorbed  by  the  chloride  of  salicyle,  producing  a yellow 
body,  which  crystallizes  from  a boiling  ethereal  solution. 
It  is  insoluble  in  water.  When  acted  upon  by  hot  acids,  it 
yields  a salt  of  ammonia  and  chloride  of  salicyle  ; an  alkali 
forms  with  it  ammonia  and  chloride  of  salicyle.  There  is 
an  analogous  bromosamide. 

Salicyluret  of  Potassium  (ESI)  is  formed  by  the  action 


What  is  the  constitution  of  salicylic  acid  ? What  is  the  action  of  am- 
^oTuced  of  salicyle  ? Under  what  circumstances  is  melahic  acid 


CINNAMYLE. 


355 


of  oil  of  meadow  sweet  on  a solution  of  caustic  potash.  It 
forms  in  yellow  crystals  from  its  alcoholic  solution,  and  has 
an  alkaline  reaction. 

Melanie  Acid  is  produced  when  the  crystals 

of  salicyluret  of  potassium  are  exposed  in  a moist  state  to 
the  air.  They  first  turn  green  and  then  black,  and  alcohol 
extracts  from  them  melanic  acid. 

CINNAMYLE. 

The  essential  oil  of  cinnamon  is  supposed  to  he  the  hy- 
druret  of  an  ideal  compound  radical,  cinnamyle,  analogous 
to  henzoyle,  and  yielding  a series. 


The  Cinnamyle  Group. 

Cinnamyle,  CisHrOg = Ci. 

Hydruret  of  cinnamyle  (oil  of  cinnamon)  . . . . = CiH. 

Oxide  “ (cinnamic  acid)  . . . . = CiO. 

Chloride  “ = CiCl. 

&c.  &c. 


Hydruret  of  Cinnamyle — Oil  of  Cinnamon  {C^^H^O^ 
+ H) — is  obtained  by  infusing  cinnamon  in  a solution  of 
salt,  and  then  distilling  the  whole.  It  is  heavier  than  wa- 
ter, and  may  be  separated  from  that  liquid  by  contact  with 
chloride  of  calcium. 

Cinnamic  Acid  [C^qH^O^-\-  O)  is  formed  when  oil  of 
cinnamon  is  exposed  to  oxygen  gas,  the  oil  becoming  a white 
crystalline  mass,  hydrated  cinnamic  acid.  It  may  also  be 
obtained  by  boiling  hard  Tolu  balsam  with  hydrate  of  lime. 
The  cinnamate  of  lime  crystallizes  as  the  solution  cools, 
benzoate  of  lime  remaining  in  solution.  The  crystals  are 
decolorized  by  animal  charcoal,  and  then  decomposed  by  hy- 
drochloric acid ; from  the  hot  solution  cinnamic  acid  crys- 
tallizes. It  melts  at  248^,  and  boils  at  5^0°.  It  is  solu- 
ble in  boiling  water  and  in  alcohol ; is  decomposed  by  hot 
nitric  acid,  and  yields  benzoic  acid,  with  oil  of  vitriol  and 
bichromate  of  potash. 

Chlorodnnose  {C^^H^Cl^O^  arises  from  oil  of  cinnamon 
by  the  substitution  of  four  atoms  of  chlorine  for  four  of  hy- 
drogen, and  is  made  by  the  action  of  chlorine  on  oil  of  cin- 
namon by  the  aid  of  heat.  It  crystallizes  from  its  alcoholic 
solution  in  colorless  needles. 

What  is  the  essential  oil  of  cinnamon  ? What  is  the  constitution  of  cin- 
namyle ? How  may  cinnamic  acid  be  prepared  ? What  is  the  constitution 
of  chlorocinnose,  and  how  is  it  prepared  ? 


350 


COMPOUNDS  OP  AMMONIA. 


LECTURE  LXXIX. 

The  Nitrogenized  Principles. — Ammonia  and  its  Salts. 
— Cyanogen. — Preparation  and  Properties  of  Prussic 
Acid.— Amy g(Mine  and  Synaptase.—  The  Cyanides. 
—Oxygen  Acids  of  Cyanogen. 

Ammonia. — I have  already  described  in  Lecture  LVI., 
the  compounds  of-hydrogen  and  nitrogen,  under  the  names 
of  sLniidogen.,  ammonia,  and  ammonium,  and  have  also  shown 
the  relation  there  is  between  the  salts  of  potash  and  soda 
and  those  of  the  oxide  of  ammonium.  This  compound  met- 
al is  a hypothetical  body ; its  existence  may,  however,  he 
illustrated  by  passing  a Yoltaic  current  through  a globule 
of  mercury  in  contact  with  moist  chloride  of  ammonium,  or 
by  putting  an  amalgam  of  mercury  and  potassium  in  a 
strong  solution  of  that  salt.  The  mercury  rapidly  increases 
in  volume,  retaining  its  metallic  aspect,  becomes  of  the  con 
sistency  of  butter,  with  a very  trivial  increase  of  weight  j 
the  resulting  substance  is  the  A/nwioniacal  A.'nicblgaTYi,  All 
attempts  to  insulate  ammonium  from  it  have  failed. 

The  most  impoitant  salts  of  ammonia  are  the  folio wino*  \ 
Chloride  of  Ammonium — ^al  Ammoniac — Muriate  of 
Ammonia— formerly  brought  from  Egypt,  but  is  now 
made  from  the  ammoniacal  liquors  resulting  from  the  de- 
structive distillation  of  animal  matters,  coal,  &c.  It  is  sol- 
uble in  watery  crystallizes  in  cubes  or  octahedrons,  and  sub- 
limes below  a red  heat  unchanged.  It  is  decomposed  by 
lime  and  potash,  and  is  formed  when  the  vapors  of  ammo- 
nia mingle  with  those  of  muriatic  acid. 

titrate  of  Ammonia  is  formed  by  neutralizing  nitric 
acid  with  ammonia.  It  is  deliquescent,  and  therefore  very 
soluble  in  water.  It  melts  at  240°,  and  at  a higher  tem- 
perature decomposes  into  steam  and  protoxide  of  nitrogen 
as  is  explained  in  Lecture  XLVI.  ’ 

Carbonates  of  Ammonia.— The  neutral  carbonate  only 
exists  in  combination.  With  the  carbonate  of  water  it 


What  is  ammonium  ? How  is  the  ammoniacal  amal gan.  prepared  ? From 
what  sources  is  sal  ammoniac  derived  ? For  what  purpose  is  nitrate  of  am 
monia  employed  ■*  a x-  i 


THE  CYANOGEN  GROUP. 


357 


unites,  forming  Bicarbonate  of  Ammonia^  which  may  he 
prepared  by  washing  the  commercial  Sesquicarbonate  with 
water  or  alcohol,  which  leaves  it  undissolved.  The  carbon- 
ate of  ammonia  of  commerce  is  prepared  by  sublimation 
from  a mixture  of  sal  ammoniac  and  chalk.  Its  constitu- 
tion is  not  uniform,  though  it  is  commonly  regarded  as  a 
sesquicarbonate. 

Suljohate  of  Ammonia  may  be  made  by  neutralizing 
sulphuric  acid  with  carbonate  of  ammonia.  It  is  soluble  in 
twice  its  weight  of  cold  water,  and  crystallizes  in  six-sided 
prisms. 

Hydroml])}iuret  of  Am^nonia  is  made  by  passing  sul- 
phureted  hydrogen  into  water  of  ammonia  until  no  more  is 
absorbed.  Though  colorless  at  first,  it  absorbs  oxygen,  and, 
sulphur  being  liberated,  it  turns  yellow.  It  is  of  consider- 
able use  as  a metallic  test. 

Cyanogen.  — Bicarburet  of  Nitrogen  — The 

mode  of  preparing  this  remarkable  body,  and  also  its  lead- 
ing properties,  have  been  described  in  Lecture  LYI.  It  is 
of  great  interest  in  organic  chemistry,  as  being  the  first  dis- 
tinctly established  compound  radical,  and  the  best  repre- 
sentative of  the  electro-negative  class  of  those  bodies. 

We  may  call  to  mind  that  it  is  easily  made  by  the  de- 
composition of  cyanide  of  mercury  at  a low  red  heat,  is  a 
gaseous  body,  soluble  in  water,  and,  therefore,  must  be  col- 
lected over  mercury.  It  is  combustible,  and  burns  with  a 
purple  flame. 


Baracyanogen  (CgiV). — When  the  cyanide  of  mercury 
is  decomposed  in  the  process  for  preparing  cyanogen,  a 
brownish  substance  is  set  free,  which  is  paracyanogen.  It 
is  insoluble  in  water  and  alcohol,  and  is  only  remarkable  in 
being  isomeric  with  cyanogen. 

Hydrocyanic  Acid — Prussic  Acid — Cyanide  of  Hydro- 

What  is  the  carbonate  of  ammonia  of  commerce  ? How  is  hydrosulphuret 
of  ammonia  made,  and  what  is  its  use  ? What  is  the  constitution  of  cya- 
nogen ? What  interesting  fact  is  connected  with  its  discovery  ? What  are 
its  properties?  What  is  paracyanogen? 


The  Cyanogen  Group. 


Cyanogen,  C^N . 
Hydrocyanic  acid 
Cyanic  acid  . . 

Fulminic  acid  . 
Cyanuric  acid  . 


= CyH. 


358 


hydrocyanic  acid. 


gm  (C2iV+ .ff).— Hydrocyanic  acid  may  be  obtained  in 
a state  of  purity  by  passing  dry  sulphureted  hydrogen  gas 
over  dry  cyanide  of  mercury  in  a tube,  and  conducting  the 
vapor,  which  is  evolved  when  the  tube  is  warmed,  into  a 
vial  iminersed  in  a freezing  mixture.  The  result  of  the  de- 
composition IS  sulphuret  of  mercury  and  hydrocyanic  acid. 
In  a state  of  aqueous  solution,  it  is  best  obtained  by  the  ac- 
tion of  dilute  sulphuric  acid  on  the  ferrocyanide  of  potas- 
sium in  a retort,  and  receiving  the  vapor  in  a Liebig’s  con- 
denser. Having  aseertained  the  strength  of  the  product,  it 
may  then  be  diluted  to  the  proper  point.  This  examina- 
tion may  be  conducted  by  precipitating  a known  weight  of 
the  acid  with  nitrate  of  silver  in  excess,  collecting  the  cya- 
nide of  silver  on  a weighed  filter,  washing,  drying,  and  re- 
Weighing,  which  gives  the  weight  of  the  cyanide.  This, 
nearly  weight  of  the  pure  hydrocyanic  acid, 

Anhydrous  hydrocyanic  acid  is  a colorless  and  very  vol- 
atile liquid,  which  exhales  a strong  odor  of  peach  blooms  • 
has  a density  of  -705  ; boils  at  79°.  It  mixes  with  wate^ 
and  alcohol  in  any  proportion.  A drop  of  it  held  in  the  air 
on  a glass  rod  becomes  solidified  by  the  rapid  evaporation 
Irom  Its  surface.  In  the  sunlight  it  decomposes  rapidly 
producing  a dark-colored  substance ; and  the  same  change 
goes  on,  though  much  more  slowly,  in  the  dark.  It  is  one 
ot  the  most  insidious  and  terrible  poisons,  a few  drops  pro- 
Queing  death  in  a few  seconds ; and  even  its  vapor,  largely 
diluted  with  air,  brings  on  very  unpleasant  symptoms.  Un- 
der the  action  of  strong  acids  it  is  decomposed  into  ammo- 
nia and  formic  acid,  the  change  being  very  simple  ■ 

C^N,  H+2,HO  = NH^  -f-  cIhO^. 

Under  such  circumstances,  hydrochloric  acid  yields  mu- 
ria,te  of  ammonia  and  hydrated  formic  acid.  Hydrocyanic 
acid  may,  to  a certain  extent,  be  preserved  from  spontane- 
mberal'^ld^^  presence  of  a minute  quantity  of  any 

Prussic  acid  may  be  detected  by  its  smell,  and  by  yield- 
ing a precipitate  of  Prussian  blue  when  acted  upon  in  so- 
lution  successively  by  sulphate  of  iron,  potash,  and  an  ex- 


How  may  hydrocyanic  acid  be  made  ? By  what  nrocess  ran 
llitZZTi  actiofofst?o®ng 

chLngeTHowmayTbeTteLl?  spontaneouf 


AMYGDALINE. 


359 


cess  of  hydrochloric  acid.  The  liquid  in  which  the  poison 
is  suspected  to  exist  should  be  acidulated  with  sulphuric 
acid  and  distilled,  and  the  hydrocyanic  acidr  will  be  found 
in  the  first  portions  which  come  over. 

Amygdaline  ( — A crystallizable  substance 

found  in  bitter  almonds,  the  kernels  of  peaches,  &c. ; is  of 
considerable  interest  in  connection  with  hydrocyanic  acid, 
inasmuch  as  these  organic  bodies  yield,  when  distilled  with 
water,  that  substance.  The  change  consists  in  the  action 
of  water  upon  amygdaline  by  the  aid  of  an  azotized  ferment 
called  Sijnaptase  or  Emuhine,  which  constitutes  the  larger 
portion  of  the  pulp  of  almonds;  the  bitter  almond  oil  at  the 
same  time  makes  its  appearance.  Amygdaline  may  be  ab- 
stracted from  the  paste  of  bitter  almonds,  from  which  the 
fixed  oil  has  been  expressed,  by  the  aid  of  boiling  alcohol, 
which  being  subsequently  distilled  off,  the  sugar  which  is 
contained  in  the  sirupy  residue  is  destroyed  by  fermentation 
with  yeast.  The  liquid  being  evaporated  again  to  a sirup, 
is  mixed  with  alcohol,  which  precipitates  the  amygdaline 
as  a 'white  crystalline  powder,  purified  by  being  redissolved 
in  alcohol  and  left  to  cool.  It  is  soluble  in  hot  and  cold 
water,  but  sparingly  soluble  in  cold  alcohol.  A weak  so- 
lution of  it  in  water,  under  the  influence  of  a small  quan- 
tity of  the  emulsion  of  sweet  almonds,  yields  at  once  oil 
of  bitter  almonds  and  hydrocyanic  acid.  When  amygda- 
line is  boiled  with  an  alkali,  it  yields  Amygdalinic  Add, 
which  forms  a salt  with  the  alkali,  and  ammonia  is  evolved. 

Cyanide  of  Potassium  {KCy)  may  be  formed  by  the 
direct  union  of  cyanogen  and  potassium,  or  by  the  ignition 
of  the  ferrocyanide  of  potassium  in  a close  vessel.  For 
common  purposes  in  the  arts  it  may  be  formed  in  a state 
somewhat  impure  by  mixing  eight  parts  of  ferrocyanide  of 
potassium,  rendered  anhydrous  by  heat,  with  three  of  car- 
bonate of  potash,  also  dry,  and  fusing  the  mixture  in  a cru- 
cible, stirring  it  until  the  fluid  part  of  the  mass  is  colorless. 
The  sediment  is  allowed  to  settle,  and  the  clear  liquid 
poured  off ; it  is  the  substance  in  question.  Cyanide  of 
potassium  is  very  soluble  in  water,  yields  colorless  octahe- 
dral crystals,  which  deliquesce  in  the  air  ; it  melts  without 

What  is  amygdaline  ? What  is  the  action  of  synaptase  and  water  upon 
it  ? How  may  it  be  obtained?  By  what  processes  may  the  cyanide  of  po* 
tassinm  be  made  ? 


860 


COMPOUNDS  OF  CYANOGEN. 


change  at  a red  heat,  and  exhales  the  odor  of  prussic  acid. 
It  is  very  poisonous. 

Cyanide  of  Mercury  may  he  made  by  dissolving  red  ox- 
ide of  mercury  in  hydrocyanic  acid,  or  by  the  action  of  a 
solution  of  ferrocyanide  of  potassium  on  sulphate  of  mercu- 
ry,  the  cyanide  crystallizing  from  the  filtered  hot  solution. 
It  forms  fine  prismatic  crystals,  more  soluble  in  hot  than 
cold  water.  It  is  poisonous ; and,  when  decomposed  at  a 
low  red  heat,  yields  cyanogen  gas. 

Cyanic  Add  {CyO  -{-  HO)  is  procured  by  heating  in  a 
retort  cyanuric  acid  deprived  of  its  water  of  crystallization  ; 
a colorless  liquid  comes  over  into  the  receiver,  which  is  the 
hydrated  cyanic  acid  ; it  has  a strong  odor  like  acetic  acid, 
and  produces  blisters  on  the  skin.  It  is  decomposed  by  the 
contact  with  water  into  bicarbonate  of  ammonia. 

C^NO,  HO  + 2HO  C^O^  + iVZZg, 

and  is  a very  instable  body,  spontaneously  changing  in  a 
short  time  into  Cyamelide,  a body  of  the  same  constitution, 
but  a white  opaque  solid,  insoluble  in  water  and  alcohol, 
and  decomposed  by  hot  oil  of  vitriol  into  carbonate  of  am- 
monia. 

Ftdminic  Acid  ( Cy^O^  + 2HO)  has  not  yet  been  insu- 
lated, but  some  of  its  salts,  presently  to  be  described,  are 
characterized  by  the  violence  with  which  they  detonate 
under  very  trivial  disturbances.  It  is  a bibasic  acid. 

Cyanuric  Acid  {Cy^O^  + 2 HO)  may  be  made  by  heat- 
ing urea,  which  disengages  ammonia ; the  residue  is  dis- 
solved in  hot  sulphuric  acid,  and  nitric  acid  added  until 
the  liquid  becomes  colorless  : on  mixing  it  with  water,  and 
allowing  it  to  cool,  the  cyanuric  acid  separates.  Its  crys- 
tals are  efflorescent ; it  is  sparingly  soluble  in  water,  and 
is  a tribasic  acid  ; and,  as  has  been  already  stated,  at  a red 
heat  it  may  be  distilled,  and  yields  cyanic  acid  without  any 
other  product. 

How  may  the  cyanide  of  mercury  be  prepared  ? Exposed  to  heat,  what 
does  it  yield  ? What  are  the  constitution  and  properties  of  cyanic  acid  ? 
What  of  fulminic  acid  ? What  of  cyanuric  acid  ? 


DERIVATIVES  OF  CYANOGEN. 


36] 


LECTURE  LXXX. 

Bodies  allied  to  Cyanogen. — Salts  of  the  Oxycyanogen 
Acids.  — F ERROC yanogen.  — Ferrocyanides  of  Hydro- 
gen and  Potassium. — Prussian  Blue  and  Basic  Blue. 
— Ferridcyanogen.  — SuLPHocYANOGEN. — Compounds 
tvith  Hydrogen  and  Potassium. — Melam^  Melamine, 

(^C. 

Cyanate  of  Potash  (/fO,  CyO)  maybe  prepared  by  ox- 
ydizing  cyanide  of  potassium  by  oxide  of  lead  in  an  earthen 
crucible ; the  result  boiled  with  alcohol  yields,  on  cooling, 
crystals  of  cyanate  of  potash,  in  thin  transparent  plates, 
which  undergo  no  change  in  dry  air,  but  with  moisture  be- 
come converted  into  bicarbonate  of  potash  and  ammonia. 

Cyanate  of  Ammonia — Urea  ( C^H^N^O,^. — The  vapor 
of  hydrated  cyanic  acid,  mixed  with  ammoniacal  gas,  yields 
cyanate  of  ammonia.  The  solution  in  water,  when  heated, 
gives  off  ammonia,  and  the  cyanate  changes  into  Urea, 
from  which  caustic  alkalies  can  not  disengage  ammonia. 
Urea  may  also  be  made  from  the  action  of  sulphate  of  am- 
monia or  cyanate  of  potash. 

Fulminate  of  Silver  {2AgO,  is  made  by  dis- 

solving silver  in  warm  nitric  acid  and  adding  alcohol.  It 
separates  from  the  hot  liquid  in  white  grains,  which,  being 
washed  in  water,  are  dried  in  small  portions  on  filtering 
paper.  It  detonates  with  wonderful  violence  when  either 
struck  or  rubbed.  It  is  sparingly  soluble  in  hot  water,  and 
crystallizes  from  that  solution  on  cooling.  It  yields,  by  di- 
gestion with  water  and  metals,  salts,  as  those  of  zinc  and 
copper. 

Fulminate  of  Mercury  {2HgO,  is  prepared  in 

the  same  manner  as  the  foregoing,  and,  like  it,  is  very  ex- 
plosive. It  is  used  for  making  percussion  caps. 

Chloride  of  Cyanogen  (CyCV)  is  prepared  by  the  action 
of  chlorine  on  moist  cyanide  of  mercury  in  the  dark.  It  is 
a colorless  gas,  soluble  in  water,  congeals  at  0®,  and  boils 

How  is  the  cyanate  of  potash  made  ? How  may  urea  be  formed  artifi- 
cially ? What  is  the  process  for  preparing  fulminating  silver,  and  what  are 
its  properties?  For  what  purpose  is  fulminate  of  mercury  used?  What 
results  from  the  action  of  chlorine  on  cyanide  of  mercury  in  the  dark  ? 

a 


3>o3 


COMPOUNDS  OF  FERROCYANOGEN. 


at  11°  ; condenses  into  a liquid  under  the  pressure  of  four 
atmospheres.  When  kept  in  this  condition,  in  sealed  tubes, 
for  a length  of  time,  it  assumes  the  solid  state,  which  form 
may  also  be  given  to  it  by  acting  on  anhydrous  hydrocyanic 
acid  by  chlorine  in  the  sun’s  rays  ; hydrochloric  acid  is 
formed,  and  the  solid  cyanide  crystallizes.  It  exhales  a pe- 
culiar odor,  melts  at  284°,  and  is  soluble  in  alcohol  and  ether 

FERROCYANOGEN. 

Ferrocyanogen  ( CqN^Fc  = Cfy)  is  an  ideal  compound 
radical. 

Hydroferrocyanic  Acid  {Cfy^  2II)  may  be  obtained  by 
decomposing  the  insoluble  ferrocyanide  of  lead  by  sulphu- 
reted  hydrogen  while  suspended  in  water.  The  solution  be- 
ing filtered,  is  to  be  evaporated  with  sulphuric  acid  in  vacuo 
until  the  acid  is  left  solid.  It  may  also  be  prepared  by 
agitating  its  aqueous  solution  with  ether,  or  by  adding  hy- 
drochloric acid  to  a strong  solution  of  ferrocyanide  of  potas- 
sium, and  then  mixing  it  with  ether,  which  precipitates  the 
acid.  It  is  soluble  in  water,  to  which  it  gives  a powerful 
acid  reaction.  It  decomposes  alkaline  carbonates  with  ef- 
fervescence, and  does  not  dissolve  oxide  of  mercury  in  the 
cold.  In  these  respects,  therefore,  it  strikingly  differs  from 
hydrocyanic  acid. 

Ferrocyanide  of  Potassium  — Prussiate  of  Potash — 
{2K,  Cfy  -f  3ZfO). — This  salt  is  made  on  the  large  scale 
by  igniting  potash,  iron  filings,  and  animal  matters  in  an 
iron  vessel ; the  mass  is  then  acted  upon  by  hot  water,  which 
dissolves  out  a large  quantity  of  cyanide  of  potassium,  which 
is  converted  into  the  ferrocyanide  by  the  iron,  and  the  fil- 
tered solution,  on  cooling,  yields  it  in  lemon-colored  crystals, 
soluble  in  four  parts  of  cold  water.  It  is  not  poisonous.  At 
a red  heat  it  decomposes,  and  yields  cyanide  of  potassium. 

It  is  a very  valuable  reagent ; with  copper  it  yields  a choc- 
olate precipitate ; with  protoxide  of  iron,  a white ; and  with 
peroxide  of  iron,  Prussian  blue. 

Common  Prussian  Blue  (f>Cfy  + 4jPe)  is  prepared  by 
precipitating  a persalt  of  iron  by  solution  of  ferrocyanide  of  * 
potassium  ; when  dry,  it  is  of  a deep  blue,  with  a lustre  of 
coppery-red.  It  is  insoluble  in  water,  is  decomposed  by  al- 

What  is  ferrocyanogen  ? How  is  hydroferrocyanic  acid  obtained  ? How 
Is  the  prussiate  of  potash  prepared  ? Is  it  poisonous  ? What  color  does  it 
give  with  protoxide  and  peroxide  of  iron  ? What  is  common  Pmssian  blue  ? 
What  is  its  composition  ^ 


COMPOUNDS  OF  FERRIDCYANOGEN. 


363 


kaline  solutions,  which  yield  alkaline  ferrocyanides,  and  pre- 
cipitate oxide  of  iron.  It  is  soluble  in  solution  of  oxalic 
acid,  and  then  constitutes  the  basis  of  blue  writing  inks, 
which  are  used  for  steel  pens.  It  is  also  much  employed 
as  a paint. 

Basic  Prussian  Blue  (^Cfy,  4jPe  + FeO^  is  formed 
when  the  white  precipitate,  yielded  by  a protosalt  of  iron 
with  ferrocyanide  of  potassium,  is  exposed  to  the  air.  As 
its  formula  shows,  it  is  common  Prussian  blue,  with  perox- 
ide of  iron.  It  differs  from  Prussian  blue  in  the  remarka- 
ble peculiarity  that  it  is  soluble  in  pure  water. 

FERRIDCYANOGEN. 

Ferridcyanogen  ^ hypothetical 

compound  radical,  which  yields  some  compounds  of  interest. 

Ferridcyanide  of  Potassium  (3  A-f-  Cfdy)  may  be  made 
by  passing  chlorine  through  a dilute  solution  of  ferrocyanide 
of  potassium  until  it  ceases  to  yield  a precipitate  wdth  a per- 
salt  of  iron.  The  liquid  being  concentrated,  yields,  on  cool- 
ing, deep-red  crystals,  the  solution  of  which  is  of  a greenish 
color.  It  gives  no  precipitate  with  peroxide  of  iron,  but 
with  the  protosalts  a bright  blue,  lighter  than  Prussian 
blue,  and  known  as  TurnhulVs  Blue. 

Cobaltocya7iogeny  a hypothetical  radical,  yielding  com- 
pounds analogous  to  the  preceding  bodies. 

Sulphocyanogen  {Csy),  a compound  radical, 

not  yet  insulated  with  certainty.  Its  formula  shows  that 
it  is  a bisulphuret  of  cyanogen. 

Hydrosulphocyanic  Acid  (GsyH)  may  be  obtained  by 
decomposing  sulphocyanide  of  lead  by  sulphureted  hydrogen 
in  water.  The  solution  is  decomposed  by  ebullition.  It 
has  the  odor  of  acetic  acid.  It  yields  with  peroxide  of  iron 
a blood-red  color. 

Sulphocijanide  of  Potassium  {KCsy)  may  be  made  by 
heating  powdered  ferrocyanide  of  potassium  with  half  its 
weight  of  sulphur  and  one  third  of  carbonate  of  potash,  and 
keeping  it  melted  for  a short  time.  The  mass  is  then  boil- 
ed with  water,  which  dissolves  out  the  sulphocyanide,  and 
the  solution  being  concentrated,  yields  prismatic  crystals  of 

For  what  purposes  is  it  used  ? In  w'hat  respect  does  basic  Prussian  blue 
differ  from  it?  What  is  the  constitution  of  ferridcyanogen?  What  is 
Turnbull’s  blue  ? What  are  cobaltocyanogen  and  sulphocyanogen?  What 
color  does  hydrosulphocyanic  acid  yield  with  peroxide  of  iron  ? By  what 
process  is  sulphocyanide  of  potassium  made  ? 


861 


MELLON  E. 


the  salt.  It  is  soluble  in  water  and  alcohol,  and  deliques- 
ces in  the  air.  It  melts  at  a red  heat.  Its  solution  with 
peroxide  of  iron  yields  a blood-red  color. 

Melam  produced  when  sulphocyanide  of 

ammonium  is  distilled  at  a high  temperature,  or  by  heating 
dry  sulphocyanide  of  potassium  with  twice  its  weight  of 
sal  ammoniac.  It  is  insoluble  in  water,  but  dissolves  in 
strong  sulphuric  acid.  When  heated,  it  yields  mellone  and 
ammonia. 

Melamine  ( CqMqWq)  is  produced  when  melam  is  dissolv- 
ed in  a hot  solution  of  potash.  It  separates  on  cooling.  It 
is  a basic  body,  uniting  with  acids. 

Ammeline  remains  in  the  solution  after  the 

melamine  has  crystallized.  It  may  be  precipitated  with 
acetic  acid. 

Ammelide  is  prepared  by  dissolving  am- 

meline in  sulphuric  acid,  and  precipitating  with  alcohol. 


LECTUUE  LXXXI. 

Mellone — U re  a.  — Mellone,  Preparation  of. — Mello- 
nides  of  Hydrogen  and  Potassium. — Natural  and  ar- 
tificial Formation  of  Urea. — Uric  Acid.— Its  Proper- 
ties.— Derivatives  of  Uric  Acid. — Parabanic,  Oooalu- 
ric,  and  Thionuric  Acids. — Alloxantine. — Purpurate 
of  Ammonia. — X.anthic  and  Cystic  Oxides. 

Mellone  — Me). — If  sulphocyanide  of  potassium 

be  acted  upon  by  chlorine  or  nitric  acid,  a yellow  powder 
is  deposited  ; this,  when  heated,  gives  off  bisulphuret  of 
carbon  and  sulphur,  and  there  is  left  a yellowish  powder, 
which  is  mellone.  The  relation  of  its  constitution  with 
cyanogen  is  obvious.  It  resists  a moderate  heat  without 
change. 

Hydromellonic  Acid  {MeH)  — By  adding  hydrochloric 
acid  to  a hot  solution  of  mellonide  of  potassium,  this  acid 
separates  as  a white  powder  on  cooling.  It  is  partially  sol- 
uble in  hot  water,  and  possesses  strong  acid  powers. 

What  results  from  the  distillation  of  the  sulphocyanide  of  ammonium? 
What  are  melamine,  ammeline,  and  ammelide  ? How  is  mellone  pre- 
pared? What  is  the  acti«*u  of  hydrochloric  acid  on  the  mellone  of  potas- 
sium ? 


UREA. URIC  ACID. 


365 


Mellonide  of  Potassium  (KMe)  maybe  prepared  by  melt- 
ing ferrocyanide  of  potassium  with  half  its  weight  of  sul- 
phur, and  adding,  when  the  fusion  is  complete,  five  per  cent, 
of  dry  carbonate  of  potash.  The  resulting  mass  is  acted  on 
by  water,  and  the  solution  being  filtered,  is  evaporated,  until, 
on  cooling,  it  forms  a mass  of  crystals,  from  which  the  sul- 
phocyanide  may  be  removed  by  alcohol,  and  the  mellonide 
left.  It  is  soluble  in  water,  and  yields,  by  double  decom- 
position with  the  salts  of  baryta,  lime,  &c.,  mellonides  of 
these  bodies,  for  the  most  part  sparingly  soluble. 

Urea  may  be  obtained  from  urine  by  add- 

ing to  it,  when  concentrated,  a strong  solution  of  oxalic  acid. 
The  precipitated  oxalate  of  urea  is  to  be  boiled  with  pow- 
dered, chalk,  and  the  filtered  solution  concentrated  until  the 
urea  crystallizes  on  cooling.  It  may  also  be  made  artifi- 
cially by  adding  to  a strong  solution  of  cyanate  of  potash  an 
equal  weight  of  dry  sulphate  of  ammonia  ; the  solution  is 
evaporated  to  dryness  in  a water  bath,  and  the  urea  dis- 
solved out  by  alcohol.  It  crystallizes  in  prisms,  very  solu- 
ble in  water,  but  permanent  in  the  air.  At  a high  temper- 
ature it  gives  off  ammonia  and  cyanate  of  ammonia,  cya- 
nuric  acid  remaining.  Urea  contains  the  elements  of  cya- 
nate of  oxide  of  ammonium,  has  neither  an  acid  nor  alkaline 
reaction,  is  decomposed  by  hot  alkaline  solutions,  with  evo- 
lution of  ammonia,  and,  by  uniting  with  two  atoms  of  wa- 
ter, yields  carbonate  of  ammonia,  a result  which  takes  place 
during  the  putrefaction  of  urine,  the  change  being  brought 
on  by  a nitrogenized  ferment — the  mucus  of  the  bladder. 
Urea  unites  with  acids,  and  forms,  with  nitric  and  oxalic 
acids,  characteristic  salts. 

Uric  Acid — Lithic  Acid  — may  be  obtain- 

ed from  the  solid  urine  of  serpents,  which,  being  boiled  in 
solution  of  caustic  potash  and  filtered,  yields  uric  acid,  by 
the  addition  of  hydrochloric  acid,  as  a white,  inodorous,  and 
sparingly  soluble  powder ; soluble  without  change  in  sul- 
phuric acid,  from  which  it  is  precipitated  by  water.  Uric 
acid  also  exists  in  human  urine,  and  appears  to  be  always 
a product  of  the  action  of  the  animal  economy.  Of  its  salts, 
the  urate  of  soda  is  interesting  ; it  is  the  chief  ingredient  of 
gouty  concretions  in  the  joints,  called  chalk-stones.  The 

How  may  urea  be  made  artificially?  What  are  its  properties?  To 
what  substance  does  it  give  rise  in  fermentation?  Under  what  circumstan- 
ces does  uric  acid  occur?  What  are  chalk-stones  ? 


366 


PAEABANIC  ACID. 


urate  of  ammonia  occurs  as  a urinary  calculus,  and  is  often 
deposited  from  urine  as  a reddish  cloud  or  powder. 

Allantoin  is  prepared  by  boiling  uric  acid 

with  peroxide  of  lead  ; the  filtered  solution,  being  concen- 
trated, deposits  prismatic  crystals  of  allantoin  on  cooling.  It 
is  soluble  in  160  parts  of  cold  water.  By  a solution  of 
caustic  alkali  it  is  decomposed  into  ammonia  and  oxalic 
acid,  assuming,  during  this  change,  the  elements  of  three 
atoms  of  water. 

Alloxan  is  made  by  the  action  of  concen- 

trated nitric  acid  on  uric  acid  in  the  cold.  The  uric  acid 
is  to  be  added  in  small  portions  successively,  until  about 
one  third  the  weight  of  the  nitric  acid  has  been  used.  An 
effervescence  takes  place,  and  there  is  left  a white  mass, 
from  which  the  excess  of  acid  is  to  be  drained.  The  sub- 
stance is  then  to  be  dissolved  in  hot  water  and  crystallized. 
Its  solution  has  an  acid  reaction  and  a bitter  taste,  and 
stains  the  skin  purple,  and,  with  a protosalt  of  iron  and  an 
alkali,  yields  a characteristic  blue  compound. 

Alloxanic  Acid  {C^HNO^  + HO)  may  be  prepared  by 
decomposing  the  alloxanate  of  baryta  by  dilute  sulphuric 
acid.  The  alloxanate  itself  is  obtained  by  the  addition  of 
barytic  water  to  a warm  solution  of  alloxan.  It  is  a strong 
acid,  decomposing  carbonates,  and  even  water,  by  the  aid 
of  zinc. 

Mesoxalic  Acid  (<^30^  + 2HO). — Mesoxalic  acid  may 
be  obtained  by  boiling  a solution  of  alloxan  with  acetate  of 
lead,  the  resulting  mesoxalate  of  lead  being  decomposed  by 
sulphureted  hydrogen.  It  is  a strong  acid,  resists  a boiling 
heat,  and  is  bibasic. 

Mykomelinic  Acid  is  prepared  by  boiling 

a solution  of  alloxan  with  an  excess  of  ammonia,  and  then 
precipitating  by  an  excess  of  dilute  sulphuric  acid.  It  is  a 
light  yellow  powder. 

Parahanic  Acid  + 2 HO)  is  formed  by  the  ac- 

tion of  strong  nitric  acid  on  alloxan,  or  uric  acid,  by  the  aid 
of  heat.  The  crystals  form  on  cooling,  and  may  be  dried 
by  draining,  and  then  recrystallized.  It  is  soluble  in  water, 
reddens  litmus,  and  forms  beautiful  prismatic  crystals. 

Under  what  form  does  urate  of  ammonia  occur?  How  may  allantoin  be 
prepared?  What  is  the  action  of  C9ld  nitric  acid  on  uric  acid?  How  is 
alloxanic  acid  prepared?  What  substance  results  from  boiling  alloxan  with 
acetate  of  lead?  How  is  mykomelinic  acid  prepared?  What  substance 
results  from  the  action  of  hot  nitric  acid  on  uric  acid  ? 


ALLOXANMINE. 


367 


Oocaluric  Acid  + HO)  may  be  made  by  de- 

composing a hot  solution  of  the  oxalurate  of  ammonia  by 
dilute  sulphuric  acid,  and  cooling  rapidly.  The  ammonia 
salt  is  itself  procured  by  boiling  a solution  of  the  parabanate 
of  ammonia,  when  it  crystallizes,  on  cooling,  in  small  nee- 
dles. Oxaluric  acid  is  a white  crystalline  powder ; it  con- 
tains the  elements  of  one  atom  of  parabanic  acid  and  three 
of  water,  and  its  solution,  by  boiling,  yields  oxalic  acid  and 
oxalate  of  urea. 

Thionuric  Acid{CQH^N2S20^2  + 2HO),  a bibasic  acid 
prepared  by  decomposing  tWnurate  of  lead  with  sulphu- 
reted  hydrogen.  It  contains  the  elements  of  one  atom  of 
alloxan,  one  of  ammonia,  and  two  of  sulphurous  acid. 

Uramile  {CqH^N^O^. — When  an  excess  of  a saturated 
solution  of  sulphurous  acid  in  water  is  mixed  with  a cold 
solution  of  alloxan,  and  an  excess  of  carbonate  of  ammonia 
with  caustic  ammonia  added,  and  the  whole  boiled,  the 
thionurate  of  ammonia  is  deposited  on  cooling.  From  this 
the  lead  salt,  used  in  the  preparation  of  the  foregoing  acid, 
may  be  obtained  by  acetate  of  lead.  The  thionurate  of  am- 
monia, with  a little  hydrochloric  acid,  being  boiled  in  a 
fiask,  there  separates  a white  body,  which  is  uramile.  It 
differs  from  thionuric  acid  in  not  containing  the  elements  of 
two  atoms  of  sulphuric  acid.  If  the  thionurate  of  ammo- 
nia is  mixed  with  dilute  sulphuric  acid  and  evaporated  in  a 
water  bath,  Uramilic  Acid  is  deposited ; it  is 

Alloxantine  is  made  when  sulphureted 

hydrogen  gas  is  passed  through  a cold  solution  of  alloxan. 
The  product  is  filtered,  washed,  and  boiled  in  water,  which 
deposits  the  alloxantine,  on  cooling,  in  transparent  rhombic 
prisms,  which  turn  red  on  exposure  to  ammonia.  This  sub- 
stance is  alloxan,  with  one  atom  of  hydrogen.  A hot  solu- 
tion of  it  is  decomposed  when  a stream  of  sulphureted  hy- 
drogen is  passed  through  it,  and  Dialuric  Acid  forms. 

Murexide — Furpurate  of  Ammonia  — 

may  be  made  by  the  action  of  dilute  nitric  acid  on  uric 
acid,  and  then  adding  ammonia,  or  by  boiling  equal  Aveights 
of  uramile  and  red  oxide  of  mercury  with  eighty  times  their 
weight  of  water,  rendered  alkaline  by  ammonia.  The  liq- 

What  is  the  relation  between  oxaluric  and  parabanic  acid  ? How  is 
uramile  prepared?  How  is  alloxantine  prepared?  What  is  the  action  of 
dilute  nitric  acid  and  ammonia  on  uric  acid?  What  is  the  color  of  the  crj*# 
tals  of  murexide  ? 


368 


THE  VEGETABLE  ACIDS. 


uid  turns  of  a deep  purple  color,  and,  when  filtered,  depos^ 
its,  on-^cooling,  crystals  of  murexide  in  square  prisms,  which, 
by  reflected  light,  are  of  a green  metallic  lustre,  and,  by 
transmitted  light,  of  a purple.  It  is  sparingly  soluble  in 
cold  water,  but  much  more  so  in  hot,  and  is  one  of  the  most 
splendid  compounds  known. 

Murexan — Purpuric  Acid. — Murexide  is  to  be  dissolv- 
ed in  a solution  of  caustic  potash,  and  dilute  sulphuric  acid 
added.  It  forms  a yellow  powder,  and,  dissolved  in  am- 
monia, gives  rise  to  the  foregoing  body. 

Xanthic  Oxide  occurs  as  a urinary  calculus 

of  a brown  color  and  waxy  aspect.  The  calculus  may  be 
dissolved  in  dilute  potash,  and  xanthic  oxide  precipitates  as 
a white  powder  by  carbonic  acid.  It  is  a waxy  body. 

Cystic  Oxide  {CqH^NS^O^  occurs  also  as  a urinary  cal- 
culus. 


LECTURE  LXXXII. 

The  Vegetable  Acids. — Tartaric  Acid,  Preparation  of. 
— Salts  of  Tartaric  Acid.— Acids  allied  to  Tartaric. 
— Citric  and  its  allied  Acids. — Malic  and  its  allied 
Acids. — Tannic  Acid. — Gallic  Acid. — Acids  allied  to 
them. 


Of  the  vegetable  acids  several  will  be  described  with 
their  associated  alkalies.  The  following  are  those  of  which 
I shall  treat  in  this  Lecture  : 


Tartaric  . . 
Paratartaric 
Pyrotartaric 
Tartralic 
Tartrelic 
Citric  . . 
Aconitic . . 

Malic  . . 

Maleic  . . 
Fumaric . . 
Tannic  . . 
Gallic  . . 

Ellagic  . . 

Pyrogallic  . 
Metagallic  . 


. Cs  £T^Oxo-}-2HO. 

. Og  H^Oiq 2HO. 

. C,  I HO. 

2Ca  H^O^o^^sHO. 
. Cs  -H4O10  -f-  HO. 
. Oi^H^Oii — 3HO. 
. C^H  O3  --  HO. 
. Ca  -\-2HO. 

. H^Oe  +2iFO. 
. C^H  Os  -h  HO. 
. CisHsO^  +3HO. 
, Ct  HOs  -\-2H0. 

. A AO4 
■ A H^Oz 
. A AOa 


How  may  murexan  be  prepared?  Under  what  circumstar  ces  do  xanthic 
oxide  and  cystic  oxide  occur  ? 


SALTS  OP  TARTARIC  ACID. 


889 


Besides  acids  such  as  these,  which  constitute  a very  nu- 
merous group,  there  is  another  class,  which  pass  under  tha 
name  of  Coupled  Acids,  the  peculiarity  of  which  is,  that 
they  consist  of  an  acid  affixed  or  coupled  to  another  body, 
which,  without  affiecting  the  neutralizing  power  of  the  acid, 
accompanies  it  in  all  its  combinations.  Thus,  hyposulphuric 
acid  couples  with  naphthaline  to  form  hyposulphonaphtha- 
lic  acid,  which  neutralizes  just  as  much  of  any  base  as  hy- 
posulphuric acid  could  do,  the  naphthaline  not  changing  its 
powers. 

Tartaric  Acid  ( — A bibasic  acid  which 

occurs,  as  has  been  already  stated,  in  the  juice  of  grapes  and 
other  fruits  as  bitartrate  of  potash.  It  may  be  obtained  by 
dissolving  cream  of  tartar  in  boiling  water  and  adding  pow- 
dered chalk,  a tartrate  of  lime  precipitating.  The  rest  of 
the  tartaric  acid  may  be  obtained  from  the  solution  by  the 
addition  of  chloride  of  calcium,  which  yields  another  portion 
of  tartrate  of  lime,  which  may  be  decomposed  by  digesting 
with  an  equivalent  proportion  of  dilute  sulphuric  acid.  The 
concentrated  and  filtered  solution  yields  crystals  acid  to  the 
taste,  inodorous,  and  soluble  both  in  water  and  alcohol ; the 
solution  decomposes  by  keeping.  Tartaric  acid  yields  sev- 
eral valuable  salts. 

Tartrate  of  Potash — Soluble  Tartar  {2KO, 

— may  be  made  by  adding  carbonate  of  potash  to  cream  of 
tartar.  It  is  very  soluble. 

Bitartrate  of  Potash  — Cream  of  Tartar  {KO^  HO, 
CgJT^Ojo)- — This  is  the  salt  which  is  deposited  from  the 
juice  of  the  grape  during  fermentation,  as  Argol.  It  may 
be  purified  from  the  coloring  matter  it  contains  by  solution 
in  hot  water,  and  the  action  of  animal  charcoal.  In  cold 
water  it  is  very  sparingly  soluble.  It  yields  black  flux 
when  ignited  in  a close  vessel,  the  black  flux  being  carbon- 
ate of  potash  enveloped  in  carbonaceous  matter. 

Tartrate  of  Potash  and  Soda — Pochelle  Salt — Salt  of 
Seignette  {KO,  NaO,  C^HJ^^q-\-\QHO) — may  be  pro- 
cured by  neutralizing  a solution  of  the  foregoing  salt  with 
carbonate  of  soda.  On  evaporation  and  cooling  it  separ- 
ates in  large  prismatic  crystals. 

Tartrate  of  Antimony  and  Potash  — Tartar  Emetic 

What  are  coupled  acids?  From  what  source  is  tartaric  acid  derived? 
What  is  soluble  tartar?  From  what  source  is  cream  of  tartar  derived? 
What  is  Rochelle  salt  ? 

a 2 


370 


SALTS  OT  TARTAHIC  ACID. 


{KOSb^O^,  C^H^O^^+2HO).—Th\s  valuable  medicinal 
agent  is  made  by  boiling  oxide  of  antimony  with  a solution 
of  cream  of  tartar ; on  cooling,  the  crystals  are  deposited. 
They  are  much  more  soluble  in  hot  than  in  cold  water,  and 
dissolve  without  decomposition. 

Racemic  Acid — Paratartaric  Acid. — This  remarkable 
acid,  which  has  the  same  constitution  as  tartaric  acid,  and 
resembles  it  very  closely,  is  found  in  the  grapes  of  certain 
parts  of  Germany  and  France.  Racemic  acid,  however, 
differs  from  tartaric  in  yielding  a precipitate  with  a neutral 
salt  of  lime. 

Pyrotartaric  Acid  is  obtained  by  the 

destructive  distillation  of  tartaric  acid,  coming  over  with  a 
variety  of  other  products. 

The  action  of  heat  on  tartaric  acid  is  remarkable.  When 
exposed  to  a temperature  of  400°  F.,  it  melts,  throws  off 
water,  and  yields  in  succession  three  different  acids,  tartra- 
lic,  tartrelic,  and  anhydrous  tartaric  acid,  the  constitution 
of  which,  compared  with  tartaric  acid,  is  as  follows: 

Tartaric  acid -j-  2HO. 

Tartralic  “ 2C8JT4O10  + 3i?0. 

Tartrelic  “ Cgi^iOio-i-  HO. 

Anhydrous  tartaric C^H^^Oiq. 

All  these,  by  the  continued  contact  of  water,  pass  back  into 
the  condition  of  tartaric  acid. 

Citric  Acid  (C'12^5^11  + ^dlO),  a tribasic  acid,  occur- 
ring abundantly  in  the  juice  of  lemons  and  other  sour  fruits, 
and  separated  therefrom  by  the  aid  of  chalk  and  sulphuric 
acid.  It  is  clarified  by  digestion  with  animal  charcoal,  and 
yields  prismatic  crystals  of  a pleasant  taste,  and  soluble  both 
in  hot  and  cold  water.  The  crystals  are  of  two  different 
forms,  according  to  the  conditions  of  their  formation ; those 
which  separate  in  the  cold  by  spontaneous  evaporation  con- 
tain five  atoms  of  water,  three  of  which  are  basic ; but  those 
which  are  deposited  from  a hot  solution  contain  only  four. 

The  citrates  form  a very  numerous  family  of  salts,  for,  as 
the  acid  is  tribasic,  we  may  have  them  with  three  atoms  of 
metallic  oxide,  or  two  of  oxide  and  one  of  water,  or  one  of 
oxide  and  two  of  water,  besides  subsalts. 

Aconitic  Acid — Equisetic  Acid  {C^HO^  + HO) — is 

■How  is  tartar  emetic  prepared?  What  is  the  relation  between  racemic 
and  tartaric  acids  ? Describe  the  action  of  heat  on  tartaric  acid.  From 
what  source  is  citric  acid  obtained  ? How  many  classes  of  salts  does  citric 
acid  yield?  What  substano©  results  from  the  fusion  of  citric  acid? 


MALie  ACID. TANNIC  ACID.  371 

formed  by  fusing  citric  acid,  and  the  resulting  brown  prod- 
uct is  dissolved  in  water,  the  change  being 

^C,HO,)  + 5{HO), 

that  is,  one  atom  of  hydrated  citric  acid  yields  three  of  aco- 
nitic  acid  and  five  of  water.  Acoiiitic  acid  is  remarkable 
from  occurring  naturally  in  the  Aconitmn  Napellus  and 
Equisetum  Fluviatile. 

Malic  Acid  (CgJZ^Og  + 2HO),  a bibasic  acid,  occurring 
in  the  juice  of  apples  and  other  fruits.  It  may  also  be  pre- 
pared from  the  stalks  of  rhubarb,  in  which  it  occurs  with 
oxalate  of  potash.  It  is  a colorless  solid,  soluble  in  water, 
the  solution  changing  by  keeping.  When  heated  in  a re- 
tort, it  melts,  and  then  boils,  emitting  a volatile  acid,  the 
Maleic  Acid,  CqH^Oq  + 2 HO,  which  condenses  with  the 
water  in  the  receiver ; at  the  same  time  there  forms  in  the 
retort  crystalline  scales  of  Fumaric  Acid,  CJHO^  + HO 
which  may  be  separated  from  the  unchanged  malic  acid  by 
solution  in  cold  water.  It  is  to  be  observed  that  maleic 
fumaric,  and  aconitic  acids  are  isomeric  bodies. 

Tannic  Acid  {C-^qH^O^  + ZHO). — An  astringent  prin 
ciple  found  in  the  bark  of  the  oak,  nut-galls,  and  ^ig,  278. 
other  vegetable  productions.  It  may  be  separ- 
ated by  placing  in  a vessel,  b,  Fig.  278,  pow- 
dered galls.  On  pouring  on  them  sulphuric 
ether,  a liquid  drops  through  the  funnel  tube, 
c,  into  the  bottle,  a,  spontaneously  separating 
into  two  portions ; the  lower,  which  is  a solu- 
tion of  tannic  acid  in  water,  is  to  be  decanted 
and  evaporated  in  the  presence  of  sulphuric 
acid  in  vacuo.  It  yields  tannic  acid,  or  tannin, 
in  the  form  of  an  uncrystallized  mass.  This 
acid  is  soluble  in  water,  but  much  less  so  in 
ether,  has  an  astringent  taste  and  reddens  lit- 
mus paper.  With  the  persalts  of  iron  i*t  yields 
a characteristic  and  valuable  precipitate  of  a black  color, 
the  basis  of  common  writing  ink.  It  forms  insoluble  com- 
pounds with  starch,  gelatine,  and  other  organic  bodies,  that 
with  gelatine  being  of  considerable  interest.  It  is  the  basis 
of  leather.  From  the  characteristic  precipitate  it  gives 

Prom  what  sources  is  malic  acid  derived?  What  two  acids  are  yielded 
by  it  under  the  action  of  heat?  What  is  the  relation  between  maleic,  fu- 
marie,  and  aconitic  acids  ? How  is  tannic  acid  made  ? What  color  does 
•t  yield  with  persalts  of  iron  ? What  is  the  basis  of  leather? 


872 


GALLIC  ACID. 


with  that  metal,  it  is  used  as  a test  for  iron,  which  must, 
however,  he  in  the  state  of  peroxide,  as  the  protosalts  are 
unacted  upon.  The  gradual  darkening  of  pale  writing  inks 
is  due  to  the  gradual  oxydation  of  the  iron  they  contain. 

Catechin  — There  is  a body  extracted  by  hot 

water  from  catechu,  called  catechin.  It  crystallizes  in  nee- 
dles, and  does  not  form  an  insoluble  compound  with  gela- 
tine, and  gives  a green  color  with  persalts  of  iron.  By  the 
•action  of  caustic  potash  in  excess,  it  yields  a black  and  in- 
soluble substance.  Japonic  Acid.  By  the  action  of  carbon- 
ate of  potash,  it  yields  Kuhinic  Acid. 

Gallic  Acid  {Cr^HO^  + 2UO)  may  be  formed  by  ex- 
posing a solution  of  tannic  acid  to  the  air,  or  by  making 
powdered  galls  into  a paste  with  water,  and  keeping  it  ex- 
posed in  a warm  place  to  the  air  for  some  weeks.  The 
mass  is  then  pressed  and  boiled  with  water.  On  cooling, 
the  solution  precipitates  a quantity  of  gallic  acid,  which  may 
be  purified  by  recrystallization.  Like  tannic  acid,  this  sub- 
stance yields  no  precipitate  with  a protosalt  of  iron,  but  a 
deep  blue-black  with  a persalt.  It  does  not,  however,  pre- 
cipitate gelatine.  Its  crystals  are  soluble  in  one  hundred 
parts  of  cold  and  three  parts  of  boiling  water.  The  solu- 
tion has  an  astringent  taste. 

Tannic  acid  passes  into  gallic  acid  by  oxydation,  carbonic 
acid  and  water  being  evolved. 

Cjs/isOiz  +0,...^...  + 2HO)  + 2{HO) 

+ 4(C'02); 

that  is,  one  atom  of  tannic  acid  and  eight  of  oxygen  yield 
two  of  gallic  acid,  two  of  water,  and  four  of  carbonic  acid. 

Ellagic  Acid  or  gallic  acid  minus  one  atom  of 

water,  may  be  extracted  after  the  removal  of  gallic  acid  by  an 
alkali,  and  precipitated  as  a gray  powder  by  hydrochloric  acid. 

Fyrogallic  Acid  (Cg-fZgOg)  sublimes  when  gallic  acid  is 
heated  in  a retort  to  *420°.  It  is  in  the  form  of  white  crys- 
tals, which  are  soluble  in  water.  It  strikes  a black  color 
with  the  protosalts  of  iron. 

Metagallic  Acid  is  formed  when  gallic  acid 

is  suddenly  heated  in  a retort  to  500^.  It  is  a black  mass, 
insoluble  in  water,  but  soluble  in  alkalies,  from  which  it  is 
precipitated  as  a black  powder  by  acids. 

From  what  cause  do  pale  writing  inks  darken  ? What  is  catechin  ? How 
inay  gallic  acid  be  prepared  ? How  is  ellagic  acid  procured  ? What  is  the 
action  of  heat  on  gallic  acid  ? 


VEGETABLE  ALKALIES. 


373 


LECTURE  LXXXIIL 

The  Vegetable  Alkalies. — General  Properties  of  Vege^ 
table  Alkalies. — Morphia. — Its  Preparation  and  Prop- 
erties. — Other  Alkalies  of  Opium. — Meconic  Acid. — . 
Alkalies  of  Bark,  Quina,  Cinchona,  Spc. — Kinic  Acid 
— Strychnia  and  Brucia. — Table  of  Alkcdoids. — Arti- 
ficial Alkaloids. 

The  vegetable  alkalies  constitute  an  extensive  class  of 
bodies,  which  are,  for  the  most  part,  the  active  medicinal 
agents  of  the  plants  in  which  they  occur.  They  are  gener- 
ally sparingly  soluble  in  water,  but  more  soluble  in  boiling 
alcohol,  of  a bitter  taste,  and  characterized  by  containing 
nitrogen.  In  their  natural  state  they  are  united  with  an 
acid,  and,  possessing  basic  properties  in  a very  marked  man- 
ner, neutralize  acids  completely.  This  quality  seems  to  de- 
pend on  the  nitrogen  they  contain,  and  has  no  reference  to 
their  oxygen,  for  the  quantity  of  this  latter  element  which 
may  be  present  seems  to  have  no  relation  to  their  neutral- 
izing power,  and,  indeed,  in  some  of  them  it  is  not  present 
at  all.  In  many  respects  they  are  analogous  to  ammonia, 
their  salts,  unlike  those  of  some  of  the  compound  radicals, 
such  as  ethyle,  &c.,  undergoing  decomposition  in  the  same 
manner  as  the  salts  of  ammonia.  Thus  the  chloride  of 
ethyle  does  not  decompose  the  nitrate  of  silver,  but  the  an- 
alogous compounds  of  ammonia  and  vegetable  alkalies  do  ; 
and  these  bodies  may  therefore  be  separated  from  the  nat- 
ural combinations  in  which  they  occur  precisely  as  we 
should  separate  lime,  or  potash,  or  magnesia  in  their  salts. 
Most  of  the  vegetable  alkalies  are  poisonous  bodies,  and,  in- 
deed, among  them  we  meet  with  some  of  the  most  terrific 
poisons  known.  There  are  several  recently-discovered  ar- 
tificial substances,  such  as  Aniline,  and  those  containing 
arsenic  and  platinum,  which  ought  to  be  classed  with  these 
basic  bodies. 

Of  the  numerous  vegetable  alkalies,  those  which  I shall 
now  describe  are  the  most  important. 

What  are  the  vegetable  alkalies  ? What  element  do  they  all  contain  \ 
In  what  condition  are  they  commonly  found  ? What  are  their  relations  to 
acid  bodies  ? What  are  their  general  properties  ? Have  any  of  them  beei 
made  artificially  ? 


S74 


MORPHIA.— NARCOTINfi. 


Morphia  {C^^H^qNOq  + 2HO). — -This  substance  is  the 
active  principle  of -opium,  and  was  the  first  discovered  of 
these  alkalies.  It  was  insulated  by  Sertuerner  in  1803.  It 
may  be  prepared  by  mixing  a concentrated  infusion  of  opium 
with  a solution  of  chloride  of  calcium  in  excess  ; the  mix- 
ture, when  warmed,  deposits  a precipitate  of  meconate  and 
sulphate  of  lime,  and  the  hydrochlorate  of  morphia  remains 
in  solution.  From  this  it  may  be  crystallized  by  evapora- 
tion, and  a dark  liquor,  containing  narcotine  and  coloring 
matter,  separated  by  pressure  in  a piece  of  flannel.  The 
impure  hydrochlorate  may  be  re-dissolved  and  re-crystal- 
lized, and,  by  repeating  the  operation,  or  resorting  to  ani- 
mal charcoal,  it  may  be  obtained  quite  white.  The  salt 
may  now  be  dissolved  in  hot  water  and  acted  on  by  an  ex 
cess  of  ammonia,  which  throws  down  pure  morphia  as  a 
white  precipitate.  It  may  be  obtained  in  crystals  by  solu- 
tion in  alcohol. 

Morphia  is  almost  insoluble  in  water  ; it  neutralizes  acids, 
and  forms  crystallizable  salts.  Its  solution  is  bitter.  It 
dissolves  readily  in  dilute  acids,  and  yields  a deep  orange- 
red  color  when  acted  on  by  strong  nitric  acid.  The  most 
common  of  its  salts  are  the  hydrochlorate,  the  sulphate,  and 
the  acetate. 

Narcotine  is  associated  with  morphia  in 

opium.  It  may  be  obtained  by  digesting  the  insoluble  por- 
tion witli  dilute  acetic  acid ; the  precipitate  produced  by 
ammonia  is  to  be  dissolved  in  alcohol,  and  purified  by  an- 
imal charcoal.  It  yields  prismatic  crystals,  insoluble  in  wa- 
ter, and  is  a weak  base.  By  the  action  of  peroxide  of  man- 
ganese and  sulphuric  acid,  and  by  bichloride  of  platinum, 
it  yields  an  extensive  series  of  bodies,  some  of  which  are 
acids  and  others  bases. 

Codeine  — The  hydrochlorate  of  morphia, 

prepared  as  above  described,  contains  this  base  ; and  when 
the  precipitation  with  ammonia  is  made,  it  remains  in  solu- 
tion. When  pufe,  it  crystallizes  in  octahedrons,  and  is  a 
powerful  base.  Along  with  this  body,  in  opium,  there  oc- 
casionally occur  other  substances  of  less  importance,  as  The- 
baine,  P seudomorphine,  Narceine,  and  Meconine. 

Meconic  Acid  3iTO). — A tribasic  acid,  asso- 

From  what  is  morphia  obtained?  When  was  it  discovered?  Give  a 
process  for  its  preparation.  How  is  narcotine  prepared  ? What  are  its 
properties  ? What  other  alkaline  bodies  are  obtained  from  opium  ? 


CimNA. — CINCHONA. 


375 


ciated  with  morphia  in  opium.  It  may  be  obtained  from 
the  meconale  of  lime,  which  precipitates  in  the  preparation 
of  morphia  by  mixing  it  with  warm  dilute  hydrochloric 
acid,  and  repeating  the  operation  until  all  the  lime  is  re- 
moved. When  purified  from  coloring  matter,  it  crystallizes 
in  scales,  which  are  soluble  in  water  and  alcohol.  When 
heated,  it  loses  six  atoms  of  w'ater  of  crystallization  ; and  if 
its  solution  be  boiled,  or  the  dry  acid  heated  in  a retort, 
Comenic  Acid,  2HO,  a bibasic  acid  forms  with 

the  disengagement  of  water  and  carbonic  acid.  Meconic 
acid  yields,  with  the  persalts  of  iron,  a blood-red  solution. 
It  forms  several  series  of  salts,  like  all  tribasic  acids. 

Comenic  acid,  when  heated,  yields  carbonic  acid  and  a 
new  body,  Pyromeconic  Acid,  with  a small  quantity  of  an- 
other substance,  parameconic  acid.  Pyromeconic  acid  is 
composed  of  HO. 

Quina — Quinine  — This,  which  is  one  of 

the  most  valuable  of  the  vegetable  alkalies,  is  obtained  from 
Cinchona  Bark,  The  decoction  of  the  ground  bark  in  di- 
lute hydrochloric  acid  is  to  be  boiled  in  an  excess  of  milk 
of  lime,  and  the  precipitate  acted  upon  by  boiling  alcohol; 
on  evaporation  Cinchona  is  deposited  in  crystals,  but  the 
quina  remains  in  solution.  It  may  be  precipitated  by  the 
addition  of  water,  and  obtained  in  crystals  from  the  spon- 
taneous evaporation  of  its  solution  in  absolute  alcohol. 
Q,uina  neutralizes  acids  perfectly,  giving  rise  to  salts,  of 
which  the  hydrochlorate,  phosphate,  sulphate,  &c.,  are  em- 
ployed in  medicine.  It  is  sparingly  soluble  in  water,  but 
very  soluble  in  alcohol  or  acids.  The  basic  sulphate  of  qui- 
na, a common  preparation,  is  sparingly  soluble  in  water, 
but  the  neutral  sulphate  is  much  more  so.  For  this  reason, 
sulphate  of  quina  is  often  dissolved  in  dilute  sulphuric  acid. 

Cinchona  ((712^12-^^)- — This  alkali  is  obtained,  as  just 
stated,  in  the  preparation  of  quina,  with  which  it  is  asso- 
ciated in  bark,  and  is  found  in  large  quantity  both  in  the 
gray  and  red  bark.  It  crystallizes  in  prisms,  is  sparingly 
soluble  in  water.  Its  salts,  like  those  of  the  foregoing,  are 
very  bitter. 

Tw'o  other  analogous  bodies  exist  in  different  species  of 
bark.  They  are  Chinoidine  and  Aricine. 

How  is  meconic  acid  procured  ? What  is  the  action  of  heat  upon  it  ? 
What  color  does  meconic  acid  yield  with  persalts  of  iron  ? When  come- 
nic acid  is  heated,  what  acids  does  it  yield f From  what  source  is  quina 
derived  ? How  is  cinchona  prepared  ? What  other  alkalies  exist  in  bark  ? 


376 


STRYCHNIA. BRUCIA. 


Kinic  Acid  HO)  is  associated  with  the 

foregoing  bodies  in  bark.  It  is  obtained  by  decomposing 
the  kinate  of  lime,  obtained  in  the  manufacture  of  sulphate 
of  quina  by  oxalic  acid,  filtering  the  solution  from  oxalate 
of  lime,  and  the  kinic  acid  crystallizes  on  evaporation.  It 
is  very  soluble  in  water. 

Strychnia  occurs  in  Nux  Vomica,  St.  Ig- 

natius's Bean,  in  the  poison  ZTpas  Tieute,  and  other  vege- 
table products.  It  may  be  extracted  from  nux  vomica 
seeds  by  boiling  them  in  dilute  sulphuric  acid,  and  then 
acting  with  lime  and  alcohol  as  described  in  the  case  of 
quina. 

Strychnia  requires  7000  parts  of  water  for  solution,  and 
communicates  to  it  an  intensely  bitter  taste.  It  is  one  of 
the  most  violent  poisons  known.  Its  alkaline  powers  are 
well  defined,  and  it  produces  a complete  series  of  salts.  It 
is  soluble  in  hot  alcohol,  but  not  in  ether.  The  antidote 
for  an  over-dose  of  it  is  an  infusion  of  tea. 

Brucia  {C is  associated  with  strychnia,  and, 
being  very  soluble  in  cold  alcohol,  is  readily  separated  from 
it.  It  is  also  more  soluble  in  hot  water,  and  possesses  the 
poisonous  character  of  strychnia.  These  substances  are 
found  in  union  with  Igasuric  Acid. 

The  following  table  gives  the  names  of  other  vegetable 
alkalies,  and  bodies  analogous  to  them  : 


Aconitine. 

Daturine. 

Picrotoxine. 

Antearine. 

Delphinine. 

Piperine. 

Asparagine. 

Elaterine. 

Phloridzine. 

Atropine. 

Emetine. 

Populine. 

Caffeine — Theine. 

Gentianine. 

Salicine. 

Chelidonine. 

Hesperidine. 

Solanine. 

Chinoidine. 

Hyosciamine. 

Stramonine. 

Colchicine. 

Meconine. 

Thebaine. 

Conine. 

Narceine. 

Theobromine. 

Curarine. 

Nareotine. 

Veratrine. 

Daphnine. 

Of  some  of  these  bodies,  as  nicotine  and  conine,  it  may 
be  remarked  that  they  are  volatile  oily  liquids,  which  can 
form  crystallizable  salts  and  acids.  They  both  contain  ni- 
trogen, and  are  interesting  in  their  relations  to  the  three  fol- 
lowing bodies,  which  may  be  formed  artificially. 

With  what  acids  are  these  bodies  associated?  From  what  sources  is 
strychnia  procured  ? What  are  the  properties  of  strychnia  ? What  is  the 
best  antidote  to  its  poisonous  effects  ? With  what  other  alkali  is  it  asso- 
ciated ? Mention  some  other  vegetable  alkalies  ? What  analogous  substan- 
ces have  been  formed  artificially  ? 


COLORING  BODIES. 


377 


Aniline  — This  substance  is  formed  by  tbe 

action  of  potash  on  isatine,  and  is  also  one  of  the  ingredi- 
ents of  the  oil  of  coal  tar.  It  is  an  oily  liquid,  boils  at  358^, 
and  yields  crystalline  salts  with  acids. 

Leukol  — Formed  with  the  foregoing  in  oil 

of  coal  tar,  from  which  it  may  be  separated  by  distillation. 
It  is  also  an  oily  liquid,  and  can  yield  crystallizable  salts. 

Quinoline  i^G — Formed  by  distilling  quinine  or 
strychnine  with  caustic  potash.  An  oily  liquid,  very  bitter, 
strongly  alkaline,  and  yielding  crystallizable  salts. 

Besides  these  bodies  there  are  other  artificial  bases  of  an 
analogous  nature,  but  which  differ  in  the  remarkable  par- 
ticular of  containing  platinum  and  arsenic;  such,  for  exam- 
ple, as  the  platina  bases  of  Reiset  and  Gros,  or  the  arsenico- 
platinum  radical  kakoplatyle.  The  formation  of  these  or- 
ganic bases  leads  us  to  hope  that  the  vegetable  alkalies 
themselves  will  hereafter  be  artificially  formed. 


LECTURE  LXXXIV. 

The  Coloring  Bodies. — General  Properties  of  Coloring 
Principles. — Madder. — Hcematoxyline. — Carihamine, 
— Yelloio  Colors.  — Chlorophyll.  — Indigo. — Sulphin- 
digotic  Acid.  — Deoxydized  Indigo.  — Action  of  Heat 
and  Reagents  on  Indigo. — Litmus. — Carmine.  ^ 

The  coloring  principles  derived  from  the  organic  kingdom 
may  be  conveniently  divided  into  two  classes : the  non-nitro- 
genized  and  the  nitrogenized.  They  may  also  be  readily 
classed  into  groups,  as  blue,  red,  yellow,  green.  For  the 
most  part,  they  are  derived  from  vegetable  productions. 

For  some  coloring  matters,  tbe  fibres  of  those  tissues  com- 
monly employed  for  clothing  have  a sufficient  affinity  as  to 
hold  the  color  so  that  it  can  not  be  removed  by  mere  wash- 
ing, and  is  permanently  dyed.  But  in  other  instances  this 
is  not  the  case ; the  artist  then  has  to  avail  himself  of  the 
qualities  possessed  by  intermediate  bodies,  such  as  alumina 
and  the  oxide  of  tin,  which  at  once  possess  the  double  qual- 
ity of  an  affinity  for  the  coloring  matter  and  an  affinity 

What  may  be  remarked  as  respects  the  salts  of  Reiset  and  Gros  ? Hov? 
may  coloring  principles  be  classified  ? 


S78 


NON-NITROGENIZED  COLORS. 


for  the  cloth  fibre.  The  attraction  of  these  bodies  for  col- 
oring matter  may  be  illustrated  by  precipitating  alumina  in 
a solution  tinged  by  litmus ; the  solution  becomes  perfectly 
clear,  its  color  going  down  with  the  precipitate,  and  form- 
ing with  it  a lake. 

NON-NITROGENIZED  COLORING  MATTERS. 

The  ^lue  non-nitrogenized  coloring  matters  are  chiefly 
found  in  flowers  and  fruits.  They  are  reddened  by  acids, 
and  turned  green  by  alkalies. 

The  Hed  non-nitrogenizing  coloring  matters  are  of  some 
importance ; among  them  may  be  mentioned  Madder  Red^ 
the  sublimed  crystals  of  which  are  known  as  Alizarine 
Madder  also  furnishes  a purple  and  a yellow 

color. 

Hcematoxyline  is  the  coloring  matter  of 

log- wood  ; it  is  soluble  in  water  and  alcohol,  and  furnishes, 
with  iron  salts,  the  black  dye  for  hats.  The  same  principle 
is  yielded  by  Brazil-wood  and  cam- wood.  Carthamine  is  a 
very  beautiful  red,  obtained  from  safflower ; it  is  used  for 
making  pink  saucers. 

The  Yelloiv  coloring  matters.  Among  these  may  be 
mentioned  Quercitrine  HO),  derived  from  the 

Qiiercus  Tinctoria  ; Gamboge,  the  dried  juice  of  the  Gar- 
cinia  Gamhogia ; Turmeric,  used  as  a test  for  alkalies, 
which  turn  it  brown,  from  the  Curcuma  Longa;  and 
Anatto,  from  the  seeds  of  the  Bixa  Orellana. 

The  Green  coloring  matters.  Chlorophyll,  the  constitu- 
tion of  which  is  not  known.  It  is  the  green  coloring  mat- 
ter of  leaves.  It  is  insoluble  in  water,  but  soluble  in  al- 
cohol and  ether,  and  is  a fatty  substance.  It  is  also  found, 
under  very  interesting  circumstances,  in  the  animal  system 
as  the  coloring  matter  of  bile. 

NITROGENIZED  COLORING  MATTERS. 

The  nitrogenized  coloring  matters,  among  which  are  some 
of  the  most  valuable  dyes  that  we  possess,  may  also  be  di- 
vided according  to  their  tint. 

Indigo  is  derived  from  the  juice  of  several  species  of  In- 
digofer a,  and  is  formed  from  a colorless  or  yellow  compound 

From  what  source  are  the  blue  non-nitrogenized  colors  obtained  % What 
js  alizarine  ? What  are  haematoxyline  and  carthamine  ? From  what  sources 
are  quercitrine,  gamboge,  turmeric,  and  anatto  derived?  Whait  is  chlorp- 
phyll  ? From  what  soqroe  is  indigo  derived? 


INDIGO. 


379 


which  is  dissolved  out  from  the  leaves  of  these  plants  when 
they  are  allowed  to  ferment  with  water.  A deep  blue  pre- 
cipitate (indigo)  forms.  It  appears,  therefore,  to  be  a pro- 
duct of  oxydation.  It  comes  in  commerce  in  small  masses, 
which,  when  rubbed,  exhibit  a coppery  aspect,  is  insoluble 
in  water,  alcohol,  dilute  acids,  and  alkalies,  and  may  be 
sublimed,  yielding  a purple  vapor,  which  condenses  into 
ciystals  of  pure  indigo.  It  dissolves  in  about  fifteen  parts 
of  strong  sulphuric  acid,  but  still  better  in  Nordhausen  oil 
of  vitriol,  yielding  a mass  which  is  soluble  in  water.  It  is 
Sulphindigotic  Acid.  By  contact  with  deoxydizing  agents, 
blue  indigo  becomes  colorless,  as  may  be  shown  by  digest- 
ing powdered  indigo,,  green  vitriol,  hydrate  of  lime,  and 
water  together.  In  this  state,  as  in  its  natural  condition,  it 
is  soluble  in  water,  and  white  indigo  may  be  precipitated 
by  hydrochloric  acid.  On  exposure  to  the  air,  deoxydized 
indigo  absorbs  oxygen  rapidly,  and  becomes  blue  and  in- 
soluble. 

When  indigo  is  submitted  to  destructive  distillation,  it 
yields  an  oily  liquid.  Aniline,  possessed  of  powerfully  basic 
properties,  and  described  in  the  last  Lecture. 

The  relation  which  exists  between  blue  and  white  indi- 
go is  seen  from  their  formulas. 

Blue  indigo Cx^H^NO^. 

White  indigo Ci^H^NOz- 

By  several  chemists  indigo  is  regarded  as  containing  a 
radical,  Anyle,  = the  symbol  for  which  is  An.  On 

this  view',  blue  indigo  is  the  anhydrous  deutoxide  of  anyle, 
AnO^,  and  white  indigo  the  hydrated  protoxide,  AnO,  HO. 

Under  the  action  of  heat  and  of  reagents,  indigo  yields 
an  extensive  class  of  bodies,  to  which  much  attention  has 
been  given.  In  this  place  I can  do  little  more  than  enu- 
merate some  of  them.  With  dilute  nitric  acid  it  yields 
Anilic  or  Indigotic  Acid.  With  strong  nitric  acid  it  yields 
Picric  or  Carbazotic  Acid,  a substance  of  a yellow  color, 
bitter  taste,  and  forming  explosive  salts.  Heated  with  bi- 
chromate of  potash,  sulphuric  acid,  and  water,  it  yields  /m- 
tine,  which  crystallizes  in  red  prismatic  crystals,  and  con- 
tains the  elements  of  blue  indigo,  with  two  additional  atoms 
of  oxygen.  This  body,  under  the  influence  of  an  alkaline 

How  is  sulphindigotic  acid  made  ? What  is  deoxydized  indigo  ? How 
is  aniline  made  ? What  is  the  relation  between  IdIuc  and  white  indigo 
What  is  anyle  ? What  are  indigotic  acid,  carbazotic  acid,  and  isatine? 


380 


LITMUS.— CARMINE. 


solution,  unites  with  one  atom  of  water,  and  changes  into 
Imtinic  Acid.  Under  the  influence  ot  chlorine,  isatine 
yields  Chlcrrisatine,  by  an  atom  of  chlorine  substitutii»g  one 
of  its  hydrogen  atoms,  and  Bichlor isatine ^ by  the  substitu- 
tion of  two  chlorine  atoms  for  two  hydrogen  ones ; and  these, 
again,  as  in  the  case  of  isatine  itself,  acted  upon  by  alkaline 
solutions,  yield  each  an  acid.  Caustic  alkalies,  acting  on 
indigo,  yield  Crysanilic  and  Anthranilic  Acids. 

Litmus  is  derived  from  the  Rocella  Tinctoria,  Lecanora 
Tartarea,  &c.  These  lichens  yield  to  ether  a crystalline 
substance,  to  which  the  name  Lecanorine  is  given.  It  does 
not  contain  nitrogen.  It  is  in  white  crystals,  soluble  in  hot 
alcohol  and  ether.  This  substance,  heated  with  baryta  or 
alkalies,  yields  Orcine,  by  losing  two  atoms  of  carbonic  acid. 
Orcine  crystallizes  in  prisms,  which  have  a yellowish  tint 
and  a sweet  taste.  Mixed  with  ammonia,  and  exposed  to 
the  air,  oxygen  is  absorbed,  and  the  liquid  assumes  a deep 
purple  tint.  From  this  acetic  acid  precipitates  a deep-red 
powder,  Orceine^  which  contains  nitrogen,  and 

is  supposed  to*be  the  basis  of  the  dye-stuff  of  litmus.  With 
alkalies  it  gives  a blue  color.  Litmus  is  extensively  used 
in  chemistry  as  a test  for  acids  and  alkalies. 

Carmine  is  the  coloring  matter  of  the  cochineal  insect. 
Coccus  Cacti.  The  coloring  matter  may  be  obtained  from 
the  insect  by  water  or  ammonia.  The  carmine  of  commerce 
is  a lake  containing  alumina. 

Aloes  is  the  inspissated  juice  of  certain  species  of  Adoe^ 
used  as  a purgative  medicine.  When  heated  with  nitric 
acid,  and  water  added,  a yellow  precipitate  is  thrown  down, 
which,  when  purified,  is  Chrysammic  Acid.  It  yields  yel- 
low crystals  of  a bitter  taste,  and  furnishes  a solution  of  a 
purple  color.  Its  salts  are  crystallizable,  by  transmitted 
light  of  a red  color,  with  a green  metallic  reflection  like 
murexide.  The  liquid  from  which  this  acid  was  precipi- 
tated contains  picric  acid. 

What  is  the  effect  of  alkaline  solutions  on  isatine  ? What  is  the  effect 
of  chlorine  upon  it?  From  what  sources  is  litmus  derived  ? What  are  or- 
cine and  orceine?  From  what  source  is  carmine  derived?  How  is  chiys- 
ammic  acid  prepared  ? 


THE  FATTY  BODIES. 


381 


LECTURE  LXXXV. 

The  Fatty  Bodies. — Properties  of  the  Saponifiable  Fats. 
— Distinction  between  Fixed  and  Volatile  Oils. — Prep- 
aration of  Soaps. — Stearine  and  Stearic  Acid. — Mar- 
garine and  Margaric  Acid. — Oleine  and  Oleic  Acid.^ 
Margarone. — Production  of  Glycerine. — Natural  Oils, 
as  Palm  Oil,  Cocoa  Tallow,  and  Nutmeg  Butter. — 
Spermaceti. — Cholesterine. — Three  Classes  of  Volatile 
Oils. — The  Camphors. 

This  class  of  substances  is  characterized  by  several  well- 
marked  peculiarities,  and  may  be  conveniently  divided  into 
two  natural  groups,  oils  and  fats.  They  belong  both  to  the 
vegetable  and  animal  systems.  In  the  former  they  usually 
abound  in  the  seeds  or  fruits ; in  the  latter  they  are  depos- 
ited in  the  cellular  structure  of  the  adipose  tissue.  The 
natural  fats  are  usually  mixtures  of  two  or  more  ingredi- 
ents, which  differ  from  one  another  in  consistency.  In  most 
instances  they  are  stearine  and  margarine,  along  with  a liq- 
uid oleine.  These  oils  can  not  be  distilled  without  under- 
going decomposition  ; exposed  to  the  air,  they  gradually  ab- 
sorb oxygen  and  evolve  carbonic  acid.  Many  of  them,  in 
which  this  change  takes  place  with  rapidity,  turn  into  res- 
inous bodies  ; and  hence  their  application,  in  the  art  of 
painting,  as  drying  oils.  When  acted  upon  by  alkalies,  the 
fixed  oils  and  fats  give  rise  to  soaps,  and  hence  are  spoken 
of  as  Saponifiable. 

Oily  bodies  may  be  divided  into  fixed  and  volatile.  The 
fixed  oils  decompose  when  heated  ; the  volatile  ones  distill. 
A simple  test,  therefore,  is  sufficient  to  distinguish  them. 
When  a few  drops  of  an  oily  substance  are  put  on  paper, 
if  it  be  a volatile  oil  it  soon  evaporates,  and  leaves  the  pa- 
per without  a stain;  if  fixed,  the  paper  remains  greasy. 
The  fixed  oils  have  but  little  odor,  the  volatile  oils  common- 
ly a characteristic  one.  They  are  all  insoluble  in  water ; 

Into  what  natural  groups  may  the  fatty  bodies  be  divided  ? What  are  the 
natural  fats  ? What  change  do  the  drying  oils  undergo  ? How  may  the 
fixed  oils  be  distinguished  from  the  volatile  1 What  is  the  difference  of 
their  properties  1 


382 


SAPONIFICATION. 


many  of  them  are  soluble  in  alcohol ; but  in  ether  they  are 
freely  dissolved. 

By  exposure  to  a low  temperature  the  constituent  prin- 
ciples of  a mixed  oil  may  often  be  separated  from  each 
other,  the  more  solid  substances  separating  as  the  temper- 
ature descends.  When  olive  oil  is  thus  treated,  an  expo- 
sure of  40°  F.  causes  a deposit  Margarine : the  fluid  por- 
tion which  is  left  is  Oleine.  Animal  fats  exposed  to  press- 
ure between  folds  of  blotting  paper  communicate  to  it  oleine, 
atid  the  solid  residue  which  is  left  behind  is  a mixture  of 
margarine  and  Stearine.  When  the  fixed  fats  are  boiled 
with  alkaline  solutions.  Soaps  are  formed  ; these  substances, 
which  are  of  extensive  use  in  domestic  economy  and  the 
arts  from  their  detergent  qualities,  are  freely  soluble  in  wa- 
ter. In  the  process  of  making  them,  the  fats  undergo  a 
change ; they  form  true  acids,  stearine  yielding  stearic  ifcid, 
margarine  margaric  acid,  and  oleine  oleic  acid,  which  may 
be  set  free  by  decomposing  the  soap  with  an  acid.  'With 
them  there  is  also  formed  a sweet  substance.  Glycerine^ 
which  appears  to  be  the  same,  whatever  fat  may  have  been 
originally  employed.  Of  the  varieties  of  soap  met  with  in 
commerce,  Soft  Soap  is  made  from  potash,  combined  with 
whale  or  seal  oil  ; Hard  White  Soap  from  tallow  and 
caustic  soda ; Hard  Yellow  Soap  from  soda,  tallow,  palm 
oil,  and  resin.  In  the  preparation  of  white  soap  the  alka- 
line solution  is  made  to  boil,  and  tallow  added  in  small  por- 
tions until  no  more  can  be  saponified  ; the  solution  now  con- 
tains soap  and  free  glycerine  ; the  former  is  separated  by  the 
addition  of  common  salt,  in  a solution  of  which  it  is  insoluble. 
It  floats  on  the  top  of  the  liquid.  It  is  then  run  into  moulds, 
and  cut  into  bars  for  commerce.  In  this  process  the  man- 
ufacturer does  not  add  so  much  salt  as  to  separate  all  the 
water.  Commercial  soap  still  contains  from  40  to  50  per  cent. 

Stearine  may  be  obtained  from  purified  mutton  fat  by 
suffering  a warm  ethereal  solution  to  cool.  The  stearine 
crystallizes,  and  margarine  and  oleine  are  left  in  solution. 
A repetition  of  the  process  purifies  it.  It  is  a white  body, 
insoluble  in  water  and  in  cold  alcohol.  It  melts  at  130°. 
When  saponified,  it  yields  glycerine  and  stearic  acid. 


What  is  the  effect  of  a reduction  of  temperature  on  mixed  oils  ? Into 
what  may  olive  oil  be  thus  decomposed  ? What  are  soaps  ? How  may  the 
different  varieties  be  formed  ? How  is  stearine  prepared,  and  what  are  its 
properties  ? 


STEARIC  AND  MAUGARIC  ACIDS. 


383 


Stearic  Acid  {Cq^Hq^Oq)  may  be  crystallized  from  a hot 
alcoholic  solution,  is  insoluble  in  water,  and  without  taste 
or  smell.  It  is  soluble  both  in  alcohol  and  ether,  melts  at 
158°,  and  may  be  volatilized  without  change. 

Margarine. — This  substance  remains  with  oleine  in  the 
ethereal  solution  arising  in  the  preparation  of  stearine,  and 
may  be  obtained  from  it  by  evaporation  and  pressing  the 
soft  mass  in  paper.  Margarine  is  found  more  abundantly 
in  human  than  in  other  kinds  of  fat. 

Margaric  Acid  {OqqHqqOq)  is  prepared  by  saponifying 
margarine  with  potash  and  decomposing  with  hydrochloric 
acid.  It  is  also  formed  with  other  products  by  the  distilla- 
tion of  stearic  acid.  It  crystallizes  in  white  needles,  its 
melting  point  being  140*^. 

Oleine. — When  almond  or  rape  oil  is  dissolved  in  ether 
and  the  solution  exposed  to  a low  temperature,  the  marga- 
rine crystallizes,  and  oleine  may  be  obtained  by  evaporating 
the  ether.  It  remains  liquid  at  a temperature  of  0°.  From 
it  Oleic  Acid  may  be  obtained  by  saponifica- 

tion and  decomposition  with  muriatic  acid,  as  in  the  fore- 
going instances.  Its  melting  point  is  about  20°.  It  gives 
rise  to  a class  of  salts. 

Margarone  — When  a mixture  of  margaric 

acid  and  lime  is  distilled,  this  substance  is  formed,  and  car- 
bonic acid  separates.  It  is  a white  solid,  like  spermaceti, 
and  melts  at  170°. 

Glycerine  (OgHgOg). — This  substance  arises  when  any 
fatty  matter  is  saponified  with  potash,  the  soap  being  de- 
composed with  tartaric  acid,  and  dissolving  the  glycerine 
out  by  alcohol.  It  is  a colorless  liquid,  specific  gravity  1’26  ; 
it  is  soluble  in  water  and  alcohol,  but  not  in  ether.  It  may 
be  cooled  to  a very  low  point  without  assuming  the  solid 
form.  When  mixed  with  sulphuric  acid,  the  two  bodies 
unite  directly,  and  Sulpho glyceric  Acid  is  the  result : an 
acid  having  many  analogies  with  sulphovinic. 

Palm  Oil  is  brought  from  Africa,  and  much  of  it  used  in 
the  manufacture  of  yellow  soap.  It  is  of  a reddish-yellow 
color,  and  contains,  besides  oleine,  a solid  fat,  Palmitine. 
It  is  insoluble  in  water,  slightly  soluble  in  hot  alcohol,  but 


What  is  the  process  for  preparing  stearic  acid  ? How  are  margarine  and 
margaric  acid  obtained  ? What  are  the  properties  of  oleine  ? How  is  oleic 
acid  made  ? What  is  margarone  ? Under  what  circumstances  does  glvcw- 
line  form  ? What  are  palm  oil  and  palmitine  ? 


384 


FATTY  BODIES. 


very  soluble  in  ether.  Its  melting  point  is  118®.  By  sa- 
ponification and  decomposition  with  an  acid,  it  yields  Pal- 
mitic Acid,  the  melting  point  of  which  is  140°.  It  is  a 
bibasic  acid. 

Cocoa  Tallow. — A solid  fat  obtained  from  the  cocoa-nut, 
and  used  in  the  manufacture  of  candles.  Its  oleine  and 
Btearine  may  be  separated  by  pressure,  or  by  boiling  alco- 
hol, from  which  the  stearine  crystallizes  on  cooling. 

Among  other  fatty  substances  and  allied  bodies  may  be 
mentioned  Nutmeg  Butter,  which  yields,  among  other  pro- 
ducts, Myristicine,  and  by  saponification,  Myristic  Acid. 
Elaidine,  which  arises  from  the  action  of  nitrous  acid  on 
oleine  ; it  furnishes,  by  the  common  process,  Elaidic  Acid. 
Suberic  Acid,  which  arises  from  the  action  of  nitric  acid  on 
cork.  Succinic  Acid,  by  the  destructive  distillation  of  am- 
ber, or  by  the  continued  action  of  nitric  on  stearic  acid 
Sehacic  Acid,  by  the  destructive  distillation  of  oleic  acid. 
Butyrine,  Caproine,  and  Caprine,  which  are  contained 
in  butter.  These  yield,  by  saponification  and  decomposi- 
tion, Butyric,  Caproic,  and  Capric  Acids.  Butyric  acid 
can  be  made,  as  we  have  seen,  artificially  by  fermentation. 
Bees'  Wax  is  a mixture  of  two  bodies  : CeHne,  which  may 
be  dissolved  by  boiling  alcohol,  and  Myricine,  which  is  in- 
soluble therein.  Spermaceti,  which  is  obtained  from  cer- 
tain species  of  whales,  yields,  under  the  process  for  glyce- 
rine, a substance,  EtJial,  and  this,  under  the  action  of  hot 
potash,  gives  Ethalic  Acid,  with  evolution  of  hydrogen  gas. 
Cholesterine  is  obtained  from  biliary  calculi  * it  also  occurs 
in  the  substance  of  the  brain. 

The  Volatile  Oils. — These,  for  the  most  part,  are  found 
in  plants,  or  are  derived  from  them  by  simple  processes. 
Many  of  them  are  extensively  used  in  the  arts  in  the  man- 
ufacture of  varnishes,  and  others  in  the  preparation  of  per- 
fumery. Their  solutions  in  alcohol  form  Essences,  and  in 
water  Medicated  Waters.  They  are  commonly  obtained 
by  the  distillation  of  those  parts  of  the  plants  in  which  they 
occur,  with  water,  and  consist  of  two  substances,  a solid  por- 
tion, Stearopten,  or  camphor,  and  a true  oil.  They  may 
be  divided  into  groups  according  to  their  constitution. 

What  is  palmitic  acid  ? Mention  some  other  bodies  belonging  to  the 
same  class.  From  what  are  suberic,  succinic,  and  sebacic  acids  derived? 
What  bodies  are  contained  in  butter,  and  what  acids  do  they  yield  ? What 
two  substances  are  found  in  bees’  wax?  From  what  are  spermaceti  and 
cholesterine  derived  ? . 


VOLATILE  OILS. 


385 


Volatile  Oils  containing  Carbon  and  Hydrogen. 
Turpentine.  Bergamotte. 

Citron.  Cubebs, 

C'opaiva.  &c. 

Storax. 

Volatile  Oils  containing  Carbon^  Hydrogen^  and  Oxygen. 


Cajeput. 
Lavender. 
Rosemary. 
Peppermint. 


Pennyroyal. 

Valerian. 

Spearmint, 

&c. 


Volatile  Oils  containing  Sulphur. 

Black  mustard.  j Onions. 

Horseradish.  | Asafoetida. 

The  stearoptens  (camphors)  of  the  volatile  oils  are  best 
lepresented  by  common  camphor,  which  is  extracted  from 
the  Laurus  and  Dryabalonops  Camjphora  by  distilling 
with  water.  It  is  a white,  tough,  semitransparent  mass, 
lighter  than  water,  of  a well-marked  odor,  melts  at  3d0^, 
and  soon  after  sublimes  rapidly  unchanged.  Artificial 
Camjplior  is  made  by  passing  dry  muriatic  acid  gas  into  oil 
of  turpentine.  It  is  a muriate  of  oil  of  turpentine.  The 
true  camphors  originate  in  several  different  ways ; some- 
times by  the  oxydation  of  the  oils  from  which  they  are  de- 
rived ; sometimes  they  are  hydrates  of  those  oils  ; and  some 
times  they  are  isomeric  with  them. 


LECTURE  LXXXVI. 


The  Resins,  Balsams,  and  Bodies  arising  in  Destruct- 
ive Distillation. — Colojphomj,  Gum  Lac,  Amber,  Sfc. 
— India-rubber. — Balsams. — Products  of  the  Destruct- 
ive Distillation  of  Wood. — Paraffine,  Eupione,  Crea- 
sote,  and  allied  Bodies. — The  Destructive  Distillation 
of  Coal. — Naphthaline,  Paranapthaline,  Kyanol,  Car- 
bolic Acid. — Products  of  slow  Decay. — Ulmine  and  Ul- 
mic  Acid. — Crenic  and  Apocrenic  Acid. — The  Varie- 
ties of  Coal  and  other  subsidiary  Bodies. 

The  resins  are  bodies  in  many  respects  analogous  to  the 
camphors,  but  are  distinguished  from  them  by  the  circum- 
stance that  they  are  not  volatile  without  decomposition.  In 
many  instances  they  act  as  acids  ; they  all  contain  oxygen. 

Into  what  groups  may  the  volatile  oils  be  divided?  What  are  the  cam- 
phors ? What  is  common  and  artificial  camphor  ? Wliat  are  the  resins? 

R 


386 


RESINS. BALSAMS. 


Colophony  is  a mixed  resin,  obtained  by  the  distillation 
of  turpentine  with  water,  the  oil  of  turpentine  passing  over 
It  iS  a mixture  of  two  resins,  Pinic  and  Sylvie  Acids^  which 
may  be  separated  by  cold  alcohol,  in  which  sylvic  acid  is 
insoluble. 

Guin  Lac^  which  is  one  of  the  resins,  occurs  under  three 
forms  : shell  lac,  stick  lac,  and  seed  lac.  It  is  used  in  the 
preparation  of  lacquers,  and  is  the  chief  ingredient  in  seal- 
ing-wax. Among  other  resins  may  be  mentioned  Copaly 
MaUic,  Dragon's  Blood,  Gamboge,  Sandarac,  and  Dam- 
mar a Resin. 

Amber  is  a substance  belonging  to  this  class.  It  is  form- 
ed in  beds  of  bituminous  wood,  and  often  incloses  insects  in 
a state  of  beautiful  preservation.  Its  specific  gravity  is 
about  1'07.  By  distillation  it  yields  succinic  acid. 

Caoutchouc — Indian-rubher,  or  Gkim-elastic — is  the  pro- 
duct of  the  Jatropa  Elastica,  the  Heevea  Caoutchouc,  and 
several  other  tropical  trees.  The  milky  juice  which  they 
yield  is  dried  on  moulds  of  various  forms  ; it  turns  of  a black 
color  by  being  smoked.  From  its  imperviousness  to  water, 
this  substance  has  of  late  been  introduced  for  a great  va- 
riety of  purposes.  It  is  combustible,  burns  with  a bright 
flame,  is  softened  by  boiling  water,  and  still  more  so  by 
ether.  In  ether,  as  also  in  naphtha  and  coal  oil,  it  may  be 
dissolved.  Bags  of  it,  soaked  in  ether  until  they  become 
gelatinous,  may  be  distended,  by  blowing  into  them,  to  a 
very  great  size,  and  thus  become  useful  for  a variety  of 
purposes.  Very  few  chemical  agents  act  upon  India-rubber  : 
it  is  extensively  used  for  connecting  the  parts  of  chemical 
apparatus. 

Balsams  are  compounds  of  resins  with  volatile  oils ; some 
of  them  also  contain  benzoic  or  cinnamic  acids.  Some,  as 
benzoin,  are  solid ; and  others,  as  the  Balsams  of  Tolu  and 
Peru,  are  viscid  fluids. 

THE  PRODUCTS  OF  THE  DESTRUCTIVE  DISTILLATION  Ol* 
WOOD,  &c. 

When  wood  is  submitted  to  distillation  in  close  vessels,  a 
black,  inflammable  liquid  called  Tar  is  formed  ; it  contains 

What  substances  may  be  obtained  from  colophony  ? What  is  gum  lac  ? 
What  acid  does  amber  yield  by  distillation  ? Prom  what  sources  is  India- 
rubber  derived  ? What  is  the  cause  of  its  black  color  ? How  may  it  be 
softened,  and  in  what  dissolved  ? What  are  the  balsams  ? What  are  tar 
and  pitch  ? 


DESTRUCTIVE  DISTILLATION. 


387 


a great  many  remarkable  bodies,  among  which  the  following 
may  be  mentioned.  The  solid  black  residue  which  is  left 
after  the  distillation  or  inspissation  of  tar  constitutes  Pitch. 

Paraffine  {C .H)  is  obtained  by  distilling  tar,  several 
oils  coming  over  : it  is  from  the  heaviest  that  this  substance 
is  extracted.  It  is  a solid  substance,  lighter  than  water,  of 
a fatty  appearance;  it  melts  at  111°  F.,  and  distills  un- 
changed. Few  chemical  agents  act  upon  it : it  remains  un- 
changed by  the  alkalies,  acids,  &c.,  but  is  soluble  in  turpen- 
tine and  naphtha.  From  its  chemical  indifference  it  has  ob- 
tained its  name  {Parum  Affinis). 

Eupione  occurs  abundantly  in  animal  tar,  from 

which  it  may  be  prepared  by  distillation,  and  subsequently 
purified  by  rectification  from  sulphuric  acid.  From  paraf- 
fine it  may  be  separated  by  exposure  to  cold,  or,  being  more 
volatile,  by  distillation.  It  is  a colorless  liquid,  specific  grav- 
ity *074  ; it  boils  at  339°  F.  It  is  insoluble  in  water,  but 
very  soluble  in  alcohol. 

Creasote  is  extracted  from  the  heavy  oil  of  tar  by  a com- 
plicated process.  It  is  an  oily,  colorless  liquid,  of  a burning 
taste,  exhaling  a powerful  odor  of  wood  smoke.  It  is  slight- 
ly heavier  than  water,  boils  at  400°  F.,  is  combustible.  One 
hundred  parts  of  water  dissolve  about  of  this  substance, 
and  obtain  its  peculiar  odor.  It  has  the  remarkable  prop- 
erty of  coagulating  albumen  and  preserving  flesh  from  pu- 
trefactive changes.  From  this  latter  circumstance  its  name 
is  derived. 

Among  allied  substances  may  be  mentioned  Picamar^  an 
oily  liquid  of  a bitter  taste,  which  boils  at  518°  F.,  and  com- 
bines with  bases  to  form  crystalline  compounds.  Kapno- 
mar,  a colorless  liquid,  having  an  odor  of  rum  ; boils  at  360° 
F.,  and  forms,  with  oil  of  vitriol,  a purple  solution.  Cedri^ 
ret,  which  forms  red  cry&tals,  giving,  with  creasote,  a purple 
solution,  and  with  sulphuric  acid  a blue.  Pittakal,  a dark 
blue  solid,  which  yields  blue  precipitates  with  metallic  salts. 
It  contains  nitrogen. 

When  coal  tar  is  submitted  to  distillation,  like  wood  tar, 
it  yields  a volatile  oil,  which,  by  being  submitted  to  rectifi- 
cation, becomes  Coal  Oil,  or  Artificial  Naphtha.  From  it 


What  properties  distinguish  paraffine  ? What  are  the  properties  of  eu- 
pione?  What  remarkable  properties  does  creasote  possess?  From  what 
IS  its  name  derived?  From  what  sources  are  picamar,  kapnomar,  cedriret, 
and  pittakal  obtained  ? 


388 


NAPHTHALINE. 


a variety  of  substances  may  be  extracted ; they  either  pre- 
exist in  the  oil,  or  are  formed  by  the  operation. 

Naphthaline  ( is  obtained  by  rectifying  coal  gas 

tar;  it  forms  colorless  or  crystalline  plates,  melting  at  136® 
F.,  and  boiling  at  413°  F.  It  exhales  a peculiar  odor,  is 
very  combustible,  insoluble  in  water,  but  soluble  in  ether 
and  alcohol;  the  specific  gravity  of  its  vapor  is  4*528.  It 
dissolves  in  sulphuric  acid,  and  the  solution,  on  being  diluted 
with  water  and  saturated  with  carbonate  of  baryta,  yields 
two  salts,  one  containing  Sulphonaphthalic  Acid^  and  the 
other  an  acid  less  known. 

Paranaphthaline  is  associated  with  naphtha- 

line, but  differs  from  it  by  being  insoluble  in  alcohol,  by 
which  liquid  they  may  therefore  be  separated.  - 

Kyanol  an  oily  liquid,  which,  though  volatile, 

has  a boiling  point  of  358®  F.  It  is  heavier  than  water, 
with  which  it  may  be  combined,  and  is  soluble  in  alcohol 
and  ether.  It  possesses  basic  properties,  and  yields  several 
well-defined  salts.  • 

Carbolic  Acid — Hydrate  of  Phenyle  — is 

found  in  that  portion  of  oil  of  tar  which  boils  between  300® 
F.  and  400°  F.  This,  being  agitated  with  potash,  and  the 
result  decomposed  by  an  acid,  yields  carbolic  acid,  which 
may  be  purified  by  rectification  from  caustic  potash.  It  is 
an  oily  liquid,  but  may  be  obtained  in  long,  needle-shaped 
crystals.  A splinter  of  pine- wood  first  dipped  in  it  and  then 
in  strong  nitric  acid  becomes  of  a blue  color,  which  then 
passes  into  a brown.  In  many  particulars  this  substance 
resembles  creasote  so  closely,  that  a supposition  has  been 
entertained  that  they  are  in  reality  the  same  body. 

When  woody  matter  is  gradually  decomposed  by  contact 
with  air  and  moisture,  JJlmine  and  TJlmic  Acid  are  pro- 
duced. They  arise  from  a partial  oxydation,  attended  by 
the  production  of  carbonic  acid  and  water,  the  action  being 
orginally  occasioned  by  azotized  matter  in  the  wood;  cor- 
rosive sublimate,  or  any  other  body  which  possesses  the  qual- 
ity of  checking  ferment  action,  may  therefore  be  resorted 
to  to  prevent  the  dry-rot  of  wood.  When  the  access  of  air 
is  Tor  the  most  part  cut  off,  the  brown  bodies,  ulmine  and 

What  are  the  properties  of  naphthaline  ? What  substance  closely  re- 
sembles it?  What  are  the  properties  of  kyanol?  What  substance  does 
carbolic  acid  closely  resemble  ? Under  what  circumstances  are  ulmine  and 
ulmic  acid  produced  ? What  bodies  may  be  employed  to  prevent  dry-rot. 


BODIES  PRODUCED  BY  DECAY. 


389 


ulmic  acid,  no  longer  appear  alone,  but  with  them  many 
other  substances,  of  the  family  of  the  hydrocarbons,  arise. 
Besides  these,  as  in  the  formation  of  vegetable  soil  and  turf, 
azotized  acids,  such  as  the  Crenic  and  Ajpocrenic,  appear. 
These  originate  in  the  decay  of  the  nitrogenized  constitu- 
ents of  the  wood,  an  action  which  probably  precedes  its 
general  disorganization.  They  are  often  found  in  mineral 
springs,  in  combination  with  oxide  of  iron,  forming  ochery 
stains.  Crenic  acid,  by  exposure  to  the  air,  changes  into 
Ajpocrenic  Acid,  a substance  much  less  soluble  in  water. 

There  is  abundant  proof  that  all  the  varieties  of  coal 
have  originated  from  woody  fibre.  For  the  production  of 
these,  it  seems  requisite  that  the  wood  should  be  immersed 
in  water  at  a moderately  high  temperature,  and  without 
free  contact  of  air.  The  ulmine  bodies  form  from  the  decay 
of  wood  at  the  surface  of  the  earth ; the  coal  bodies  under 
a heavy  pressure.  Of  these  we  have  many  varieties,  differ- 
ing much  in  constitution  : Lignite,  which  is  of  a brown 
color,  and  in  which  the  structure  of  the  wood  is  more  or 
less  perfectly  preserved  ; the  various  forms  of  Bituminous 
Coal,  as  cannel  coal,  Newcastle  coal,  &c.  ; Anthracite, 
which  contains  but  little  hydrogen. 

With  these  more  valuable  natural  products  are  frequent- 
ly found  small  quantities  of  others  of  less  importance,  as 
Ozocherit,  or  fossil  wax  ; Idrialine,  which  is  isomeric  with 
oil  of  turpentine ; Petroleum,  or  Naphtha,  which  in  many 
Eastern  countries  is  collected  in  wells.  It  arises,  probably, 
from  the  decomposition  of  coal  by  the  action  of  the  natural 
heat  of  the  earth. 


LECTUBE  LXXXVII. 

Animal  Chemistry.^ — Equilibrium  of  the  System. — Caus- 
es of  Diminution  and  Increase. — Relation  of  Oxygen 
to  the  Food. — Digestion,  the  Nature  of  it. — Description 
of  the  Process. — Artificial  Digestion. — Two  great  Va- 
rieties of  Food. — Nutrition  in  the  Carnivora  and  Gra- 
minivora. — Routes  of  the  Passage  of  Nutritious  Mat- 
ter into  the  System. 

In  the  preceding  Lectures  I have  given  the  descriptive 

From  what  bodies  do  crenic  and  apocrenic  acids  arise  7 What  ig  th^ 
source  of  the  diiferent  varieties  of  coal  ? What  is  lignite  7 


390 


ANIMAL  CHEMISTRY. 


history  of  many  of  the  more  important  organic  compounds, 
and  chiefly  those  belonging  to,  or  derived  from,  the  vegeta- 
ble kingdom.  It  remains  now  to  mention  another  class 
which  seems  to  bear  a closer  relation  to  animal  beings. 
The  appearance  and  destruction  of  these  compounds  lead 
by  ready  steps  to  a consideration  of  the  physiological  func- 
tions of  the  animal  mechanism. 

There  are  certain  causes  which  tend  constantly  to  change 
the  weight  of  an  adult,  healthy  individual;  causes  of  in- 
crease and  causes  of  diminution.  Among  the  former  may 
be  mentioned  food,  drinks,  and  atmospheric  air ; among  the 
latter,  urine,  faeces,  transpired  and  expired  matters.  And 
these,  in  the  course  of  a year,  amount  to  many  hundred 
pounds;  yet  the  resulting  action  of  the  mechanism  is  such 
that,  at  the  end  of  that  time,  the  weight  remains  un- 
changed. 

This  fact,  the  constancy  of  adult  weight,  can,  therefore, 
only  be  explained  by  an  examination  of  the  action  of  the 
matters  introduced  into  the  interior  of  the  system  on  each 
other,  or  an  examination  of  the  matters  rendered.  What- 
ever is  fit  for  food,  when  burned  in  the  open  air,  with  free 
access  of  oxygen,  must  yield  carbonic  acid,  water,  and  am- 
monia ; and  these,  in  point  of  fact,  are  the  results  of  the  ac- 
tion of  the  animal  mechanism.  Oxygen  gas,  introduced  by 
the  respiratory  process  through  the  lungs,  effects  eventually 
the  destruction  of  the  hydrocarbons  and  nitrogenized  bodies 
which  have  been  introduced  through  the  stomach  ; and  car- 
bonic acid,  ammonia,  and  the  vapor  of  water,  or  substances 
in  a transition  state,  which  tend  eventually  to  assume  those 
forms,  are  the  result.  An  elevated  temperature  must,  as  a 
consequence,  be  obtained. 

Before  the  introduction  of  chemical  principles  into  the 
science  of  physiology,  it  was  a favorite  idea  that  the  animal 
system  possessed  the  peculiarity  of  resisting  the  influence 
of  external  agents.  This  is  an  error.  There  is  no  essen- 
tial difference  between  the  physical  effects  taking  place  in 
the  body  during  life  and  after  death,  nor  is  there  any  prin- 
ciple of  resistance  to  external  agents  possessed  by  living 
structures.  The  only  distinction  is,  that  during  life  the  ef- 
fete materials  pass  off  by  appointed  routes — -the  kidneys,  the 

What  causes  are  in  operation  tending  to  change  the  weight  of  an  adult 
animal?  Mention  some  of  the  causes  of  increase  and  some  of  diminution. 
What  is  the  chemical  nature  of  the  food  ? 


PROCESS  OP  DIGESTION  391 

lungs,  or  the  skin ; and  after  death,  these  passages  being 
closed,  they  accumulate  in  the  interior  of  the  body. 

The  matters  returned  by  an  animal  to  the  external  world 
are  all  found  to  be  oxydized  bodies,  or  such  as  arise  from 
processes  of  oxydation.  The  result  is,  therefore,  forced  upon 
us  that  the  primitive  action  of  the  mechanism  is  the  oxy- 
dation of  the  food  in  the  system  by  air  which  has  been  in- 
troduced through  the  lungs. 

The  process  of  digestion  appears  to  be  exclusively  for  the 
object  of  effecting  the  minute  subdivision  of  the  food.  By 
the  action  of  the  teeth  or  other  organs  of  mastication,  it  is 
first  roughly  divided  and  simultaneously  mixed  with  saliva. 
It  is  then  passed  into  the  stomach,  and  in  that  organ  mixes 
with  the  gastric  juice,  a viscid  and  slightly  acid  body.  This 
mixture  is  perfected  by  certain  movements  which  the  food 
now  undergoes,  and  under  the  conjoint  action  of  the  saliva 
and  the  gastric  juice  it  is  totally  broken  up  into  a gray, 
semifluid,  homogeneous  mass,  sometimes  acid  and  sometimes 
insipid,  of  the  consistency  of  cream  or  gruel,  called  Chyme. 
This  gradually  passes  out  through  the  pyloric  orifice  of  the 
stomach,  and  enters  the  intestine. 

It  has  been  a question  whether  artificial  digestion  could 
be  performed,  but  it  now  appears  to  be  universally  admit- 
ted that  an  acidulated  water,  containing  animal  matter  in 
a state  of  change,  has  the  power  of  impressing  analogous 
changes  on  organized  substances  submitted  to  its  action, 
just  as  the  gastric  juice,  containing  hydrochloric  or  acetic 
acid,  with  animal  matter  undergoing  metamorphosis,  de- 
rived from  the  saliva  or  the  coats  of  the  stomach,  possess- 
es the  power  of  dissolving  fibrin  or  coagulated  albumen. 

Soon  after  its  entrance  into  the  intestine  the  chyme  is 
mingled  with  bile  and  pancreatic  juice,  the  former  coming 
from  the  liver,  the  latter  from  the  pancreas.  The  effect 
appears  to  be  a division  of  the  chyme  into  three  parts  : 1 st. 
A creamy  fluid  ; 2d.  A whey-like  fluid  ; 3d.  A red  sedi- 
ment : the  two  former,  commingled,  constitute  what  is  des- 
ignated the  Chyle. 

What  gas  is  introduced  through  the  lungs  ? How  do  these  act  on  each 
other?  Do  animal  structures  possess  any  power  of  resisting  the  influence 
of  external  agents  ? Why  do  we  conclude  that  the  oxydation  of  the  food 
is  the  principal  effect  going  on  in  the  system?  What  is  the  object  of  di- 
gestion ? How  is  chyme  prepared  ? Can  digestion  be  conducted  artifi- 
cially? With  what  fluids  does  the  chyme  mingle?  What  is  their  action 
on  it  ? What  is  chyle  ? 


392 


PRODUCTION  OF  CHYLE. 


It  has  been  already  remarked  that  the  aim  of  the  digest- 
ive process  appears  to  be  the  subdivision  of  the  food.  It  ia 
for  this  that  the  teeth  comminute  it ; and  the  gastric  juice, 
excited  to  activity  by  the  oxygen  introduced  with  the  saliva, 
breaks  down  by  its  ferment  action  all  albuminous  and  fib- 
rinous matters,  and  prepares  the  food,  in  this  condition  of 
extreme  subdivision,  for  its  passage  into  the  blood-vessels. 

Before  we  can  trace  the  changes  which  then  occur,  it  is 
proper,  however,  to  remark  that,  as  respects  the  food  itself, 
it  may  be  distinguished  into  two  varieties  : 1st.  The  food 
of  nutrition,  or  the  nitrogenized  food  ; 2d.  The  food  of  res- 
piration, or  the  non-nitrogenized  food. 

The  nutritive  processes  of  carnivorous  animals  are  very 
simple  ; they  live  on  the  graminivora,  and  find,  in  the  car- 
cases they  consume,  the  fats,  the  fibrin,  and  other  such 
bodies  which  are  necessary  for  their  own  economy  ; these, 
therefore,  simply  require  to  be  brought  into  a state  of  solu- 
tion, or  of  extreme  subdivision,  and  then  are  absorbed  into 
the  blood-vessels.  In  these  cases  the  fats  constitute  the 
food  of  respiration,  and  the  nitrogenized  bodies  that  of  nu- 
trition. 

But  the  graminivora  find  in  the  vegetable  matters  they 
use  the  same  essential  principles  ; their  fibrin,  albumen, 
and  fats  are  directly  obtained  from  plants,  in  which  they 
naturally  occur.  In  the  digestive  process  of  the  two  great 
classes  of  animals,  there  is  not  therefore,  in  reality,  any  dif- 
ference ; both  find  in  their  food  the  elements  they  require. 

There  is  reason  for  believing  that  the  two  classes  of  food 
are  introduced  into  the  system  by  different  routes — ^the  fatty 
or  respiratory  food  passing  through  the  lacteals,  and  the  ni- 
trogenized bodies  being  taken  up  by  the  veins. 

What  two  great  varieties  of  food  are  there  ? Describe  the  nutritive  pro- 
cesses of  the  carnivora.  What  is  their  respiratory  food  ? Describe  the 
nutritive  processes  of  the  graminivora.  By  what  routes  are  the  two  v ’*’*»- 
ties  of  food  introduced  into  the  system  ? 


ORIGIN  OF  FAT. 


393 


LECTURE  LXXXVIII. 

Origin  and  Deposits  of  the  Fats  and  Neutral  Nitro- 
GENizED  Bodies. — Artificial  Formation  of  Fat. — It 
may  be  made  in  the  Animal  System,  or  directly  ah- 
sorbed  from  the  Food. — Proofs  of  the  latter. — Varieties 
of  Fat  arising  in  partial  Oxydation. — Changes  in  Fat 
as  it  passes  through  the  Systems  of  the  Graminivora 
and  Carnivora. — Its  final  Destruction. — Origin  and 
Deposit  of  the  Neutral  Nitrogenized  Bodies. — Proper- 
ties of  Fibrin,  Albumen,  Casein,  Protein,  Gelatin,  SfC. 

Two  opinions  have  been  entertained  respecting  the  origin 
of  the  fat  which  occurs  in  the  adipose  tissues  of  animals. 
1st.  It  has  been  supposed  to  be  produced  by  processes  taking 
effect  in  the  system  ; or,  2d.  Simply  collected  from  the  food. 

In  many  various  processes  fatty  bodies  arise.  Thus, 
when  flesh  meat  is  left  in  a stream  of  water,  a mass  of  ad- 
ipocere  is  eventually  found.  During  the  action  of  nitric  acid 
on  fibrin,  and  in  the  preparation  of  oxalic  acid  from  starch, 
oily  bodies  are  apparently  produced.  There  is  every  reason 
to  believe,  however,  that  these  are  rather  insulated  than 
formed,  or  that  they  pre-exist  in  the  bodies  from  which  they 
are  apparently  derived. 

But  recent  experiments,  as  in  the  preparation  of  butyric 
acid  from  sugar,  have  decisively  demonstrated  that  the  fatty 
bodies  can  be  artificially  formed  from  the  non-nitrogenized 
by  processes  such  as  those  of  fermentation,  and,  consequently, 
we  have  every  reason  to  suppose  that  the  animal  system 
can  form  fats  from  the  food,  although  none  might  occur 
there  naturally. 

But,  though  the  power  of  forming  oily  from  amylaceous 
bodies  may  be  possessed  by  the  animal  mechanism,  there 
can  be  no  doubt  that  in  many  instances  it  is  not  resorted  to, 
and  that  fats  contained  in  the  food  are  at  once  absorbed  into 
the  system.  Often  this  absorption  takes  place  with  so  slight 

What  opinions  have  been  held  respecting  the  origin  of  fat  ? In  what  pro- 
cesses is  it  apparently  produced  ? What  reason  is  there  to  believe  that  it 
can  be  formed  from  the  starch  bodies  ? What  reason  is  there  for  believing 
that  many  fats  are  directly  absorbed  into  the  system  ? 

R 2 


394 


ABSORPTION  OP  FAT. 


a change  impressed  upon  the  oil,  that  without  difficulty  we 
can  detect  its  presence  by  its  odor  or  its  taste.  Thus  the 
milk  of  cows  which  are  fed  on  linseed  cake  tastes  strongly 
of  that  substance  ; and  at  those  seasons  of  the  year  when 
such  animals  feed  on  young  shoots  or  leaves  containing 
odoriferous  oils,  the  taste  is  at  once  detected  in  the  milk. 

The  deposition  of  fat  upon  an  animal,  and  the  production 
of  butter  in  its  milk,  bear  a certain  relation  to  the  amount 
of  oleaginous  matters  found  in  its  food.  For  this  reason, 
Indian  corn,  which  contains  from  eight  to  twelve  per  cent, 
of  oil,  furnishes  one  of  the  most  available  articles  for  feed- 
ing and  fattening  cattle.  It  is  now,  however,  admitted, 
that  where  foods  without  fat  are  used,  the  system  possesses 
the  power  of  effecting  their  production  ; thus  bees  will  pro- 
duce wax  though  fed  upon  pure  sugar,  and  animals  will 
grow  fat  though  fed  on  potatoes  alone. 

A great  number  of  the  fatty  bodies  may  be  derived  from 
inargaric  acid  by  processes  of  partial  oxydation.  With  a 
limited  supply  of  oxygen  gas,  ethalic  and  myristic  first  make 
their  appearance  ; and  the  supply  being  still  continued, 
there  follow  cocinic,  1 auric,  &c.,  the  process  being  as  shown 
in  the  following  table  : 


These  partial  oxydations  being  perfected,  there  result  at  last 
carbonic  acid  gas  and  water,  the  same  bodies  which  appear 
when  a fat  is  directly  burned  in  the  open  atmospheric  air. 

The  fats  which  occur  in  plants  pass  into  the  systems  of 
graminivorous  animals,  and  there  undergo  changes,  a series 
of  partial  oxydations  occurring.  It  is  only  a part  which  is 
completely  destroyed  so  as  to  produce  carbonic  acid  and  wa- 
ter, and  this  part  is  the  element  of  respiration.  The  res- 
idue accumulates  in  the  cells  of  the  adipose  tissues,  and,  de- 
voured by  the  carnivorous  tribes,  is  destined  to  undergo  in 
them  those  successive  changes  which  bring  it  back  to  the 

Is  there  any  relation  between  the  production  of  butter  and  the  quantity 
of  oil  in  the  food  ? Can  bees  form  wax  from  sugar?  By  what  process  can 
the  fatty  bodies  be  derived  from  each  other  ? In  what  do  these  partial  ox- 
ydations terminate  at  last  ? What  change  occurs  to  vegetable  fats  in  pass- 
ing through  the  systems  of  the  grarninivora?  What  is  the  object  of  the  en- 
tire combustion  of  a portion  of  it  ? By  what  means  is  the  residue  at  last 
brought  to  the  same  state  ? 


Margaric. 

Ethalic. 

Myristic. 

Cocinic. 

Laurie. 


CEnanthytio. 

Caproic. 

Valerianic. 

Butyric. 


Capric. 


FIBRIN, ALBUMEN. 


395 


condition  of  carbonic  acid  and  water,  and  restore  it  to  the 
atmosphere  from  which  it  was  originally  derived  by  plants. 

The  amylaceous  bodies  and  fats,  or  the  non-nitrogenized 
bodies,  are,  therefore,  the  food  of  respiration  ; their  office  is 
to  neutralize  the  oxygen  introduced  by  the  lungs,  and,  by 
the  production  of  carbonic  acid  gas  and  water,  keep  up  the 
temperature  of  the  animal  system. 

I have  already  described  the  fatty  bodies,  and  given  the 
history  of  their  general  properties.  It  is  unnecessary  to  re- 
peat here  what  has  been  already  said. 

When  the  expressed  juices  of  plants,  such  as  beets,  tur- 
nips, &c.,  are  allowed  to  stand,  t|iere  is  deposited,  after  a 
short  time,  a coagulum  or  clot,  which  does  not  appear  to 
differ  in  any  respect  from  animal  Fibrin.  If  this  be  re- 
moved, and  the  temperature  of  the  juice  raised  to  212°  F., 
it  becomes  turbid  again,  from  the  deposit  of  a second  body. 
Albumen,  On  separating  this  and  slowly  evaporating,  a 
film  forms  on  the  surface,  identical  with  Casein.  These 
three  bodies  contain  nitrogen,  and  may,  therefore,  be  looked 
upon  as  the  representatives  of  the  neutral  nitrogenized  class. 

Fibrin{C^QH^^O-^^NQ  . + {S.F) ). — This  substance  may 
be  obtained  by  beating  fresh-drawn  blood  with  twigs,  and 
washing  with  water  and  ether  the  clot  which  adheres  there- 
to. As  thus  prepared,  fibrin  is  a white,  elastic  body,  insol- 
uble in  water,  alcohol,  or  ether,  but  soluble  in  hydrochloric 
acid,  with  which  it  yields  a blue  solution.  It  possesses  the 
power  of  decomposing  rapidly  the  deutoxide  of  hydrogen. 
When  dried  it  shrinks  very  much  in  volume,  but,  for  the 
most  part,  recovers  its  bulk  when  again  moistened.  Fibrin 
derived  from  arterial  and  venous  blood  is  not  altogether  the 
same  ; the  latter  may  be  dissolved  in  a warm  solution  of 
nitrate  of  potash,  but  the  former  can  not.  In  the  formula 
annexed  to  this  body,  the  symbols  within  the  brackets  mere- 
ly mean  small  and  indeterminate  quantities  of  sulphur  and 
phosphorus. 

Albumen  occurs  abundantly  in  the  serum  of  blood  and  in 
the  white  of  eggs,  from  which  it  may  be  obtained  by  neu- 
tralizing in  a solution  of  it  the  associated  soda  with  acetic 
acid,  and  on  dilution  with  cold  water  it  falls  as  a white  pre- 
cipitate, soluble  in  water  containing  a minute  quantity  of 


What  bodies  constitute  the  food  of  respiration  ? What  is  the  composir 
tion  of  fibrin?  From  what  sources  may  it  be  derived  ? What  are  its  prop 
erties?  What  are  the  sources  and  properties  of  albumen  ? 


396 


PROTEIN  AND  ITS  DERIVATIVES. 


alkali.  Exposed  to  a sufficient  heat,  common  albumen  co- 
agulates and  becomes  a white  body,  wholly  insoluble  in  wa- 
ter. The  strong  acids  also  unite  directly  with  it,  and  form 
insoluble  compounds ; acetic  and  the  tribasic  phosphoric 
acid  are  exceptions.  With  metallic  salts,  as  corrosive  sub- 
limate, it  gives  insoluble  precipitates ; hence  its  use  as  an 
antidote  for  that  poison.  Its  constitution  is  identical  with 
that  of  fibrin,  except  that  it  appears  to  contain  twice  as 
much  sulphur. 

Casein  is  found  abundantly  in  milk.  It  is  insoluble  in 
water,  but,  like  albumen,  is  readily  dissolved  if  free  alkali 
is  present.  It  may  be  obtained  by  coagulating  milk  with 
sulphuric  acid,  and  dissolving  the  curd,  after  it  has  been 
well  washed  with  water,  in  a solution  of  carbonate  of  soda. 
By  standing  it  separates  into  two  portions,  oily  and  watery. 
From  the  latter  the  casein  is  re-precipitated  by  sulphuric 
acid,  and  the  process  repeated.  The  casein  is  finally  washed 
with  ether  to  remove  any  trace  of  fat.  It  is  a white  sub- 
stance, soluble  in  an  alkaline  water,  the  solution  not  being 
coagulated  by  boiling,  but  a skin  forms  on  the  surface  as 
evaporation  goes  on.  It  can,  however,  be  coagulated  by  cer- 
tain anim?tl  membranes,  as  by  the  interior  coat  of  the  stom- 
ach of  a calf.  It  contains  five  or  six  per  cent,  of  bone  earth. 

The  foregoing  bodies  are  sometimes  spoken  of  as  the 
Protein  group,  from  the  circumstance,  as  is  shown  in  their 
formula,  that  they  all  contain  a body  which 

passes  under  the  designation  of  protein.  It  may  be  ex- 
tracted from  them  by  dissolving  either  of  them  in  an  alka- 
line solution,  and  precipitating  by  an  acid.  It  is  a taste- 
less, white,  insoluble  body,  soluble  in  acetic  acid  and  in  al- 
kalies. It  yields  a binoxide  and  tritoxide,  which  may  be 
produced  by  boiling  fibrin  in  water  in  contact  with  air. 
These  substances  are  the  chief  constituents  of  the  huffy 
coat  of  inflammatory  blood. 

Gelatin  [C ^ is  prepared  by  dissolving  isin- 
glass in  warm  water.  It  forms,  on  cooling,  a soft  jelly, 
which  contracts  as  it  dries.  Solution  of  gelatin  is  precip- 
itated by  corrosive  sublimate,  tannic  acid,  or  infusion  of 
galls  ; with  the  latter  bodies  it  yields  a precipitate  which 
is  the  basis  of  leather.  Glue  is  an  impure  gelatin. 

What  are  the  sources  and  properties  of  casein  ? What  is  protein  ? What 
relation  has  it  to  the  foregoing  bodies  ? WTiat  oxides  does  it  give  ? How 
is  gelatin  obtained  ? What  precipitate  does  it  give  with  infusion  of  galls  ? 


ENTRANCE  OF  FOOD  INTO  THE  SYSTEM.  397 


On  examining  the  constitution  of  some  of  the  leading 
tissues  of  the  animal  system,  it  is  plain  that  they  hear  a re- 
markable relation  to  protein,  as  is  shown  in  the  following 
table  : 

Protein,  . . . . = Pr. 

Arterial  membrane = Pr  4-  HO. 

Chondrin  (rib  cartilage)  . . . = Pr4-  PO  -j- O. 

Hair,  h^ns = Pr-f-  NH^-^O^. 

Gelatinous  tissues =z2Pr  -j-  SNH^  HO 

These  different  bodies  are  therefore  derived  from  the  pro- 
tein group  by  processes  of  partial  oxydation,  for  in  their  con- 
stitution they  correspond  to  oxides,  hydrated  oxides,  &c. 

The  nitrogenized  bodies  introduced  into  the  system  pass 
through  the  same  changes  as  the  non-nitrogenized : partial 
oxydations  giving  rise  to  various  tissue  forms,  and  ending  in 
perfect  oxydation,  with  a production  of  water,  ammonia,  and 
carbonic  acid. 

Whether  we  regard  the  respiratory  or  the  nutritive  food, 
we  see  that  the  result  is  the  same.  Introduced  through 
the  blood-vessels  into  the  system,  it  is  brought  under  the 
destructive  influence  of  oxygen  arriving  through  the  lungs, 
and,  as  I have  already  explained,  the  amount  of  oxygen  is 
so  adjusted  to  the  amount  of  these  classes  of  food  combined, 
that  in  an  adult  and  healthy  individual  the  weight  does  not 
change,  even  after  the  lapse  of  a considerable  period  of  time. 


LECTURE  LXXXIX. 

Of  the  Introduction  of  Respiratory  and  Nutritious 
Food  into  the  Blood,  and  its  Transmission  through 
the  System. — Absorption  by  the  Lacteals  and  Veins. — 
Cause  of  the  Circulation  of  the  Blood.  — Constitution 
and  Properties  of  the  Blood.  — Plasma  and  Disks.  — 
The  Offices  of  each.  — The  Coagidation  of  Blood.  — 
Analysis  of  Blood. 

The  ordinary  principles  of  capillary  attraction  are  amply 
sufficient  to  account  for  the  absorption  of  nutritious  matter 
from  the  intestinal  cavity,  both  by  the  lacteal  vessels  and 

What  relation  does  protein  bear  to  other  tissues  ? What  changes  do  the 
nitrogenized  bodies  pass  through  ? What  physical  principle  is  involved  in 
the  absorbent  action  of  the  lacteals  and  veins  ? 


398 


CIRCULATION  OP  THE  BLOOD. 


the  veins  By  this  it  is  eventually  brought  into  the  gen» 
eral  current  of  the  circulation,  and  distributed  to  every  part 
of  the  system. 

With  respect  to  the  forces  involved  in  the  circulation  of 
the  blood,  most  physiologists  have  regarded  the  hydraulic 
action  of  the  heart  as  amply  sufficient  to  account  for  all  the 
phenomena.  It  is  now  on  all  hands  conceded  that  this  or- 
gan discharges  a very  subsidiary  duty.  The  whole  vege- 
table creation,  in  which  circulatory  movements  of  liquids 
are  actively  carried  on  without  any  such  central  mechanism 
of  impulsion  ; the  numberless  existing  acardiac  beings  be- 
longing to  the  animal  world ; the  accomplishment  of  the 
systematic  circulation  of  fishes  without  a heart ; and  the  oc- 
currence in  the  highest  tribes,  as  in  man,  of  special  circu- 
lations which  are  isolated  from  the  greater  one,  have  all 
served  to  demonstrate  that  we  must  look  to  other  principles 
for  the  cause  of  these  remarkable  movements. 

The  cause  of  the  circulation  of  the  blood  is  to  be  found 
in  the  chemical  relations  of  that  liquid  to  the  tissues  with 
which  it  is  brought  in  contact.  On  the  principles  of  capil- 
lary attraction,  a liquid  will  readily  flow  through  a porous 
body  for  which  it  has  a chemical  affinity,  but  it  will  refuse 
to  flow  through  it  if  it  has  no  affinity  for  it.  On  this  prin- 
ciple we  can  easily  explain  why  the  arterial  blood  presses 
the  venous  before  it  in  the  systemic  circulation,  and  why 
the  reverse  ensues  in  the  pulmonary.  This  explanation  of 
the  circulation  of  the  blood,  which  I offered  some  years  ago, 
is  now  admitted  by  many  of  the  leading  physiological  writ- 
ers to  be  true. 

The  systemic  circulation  takes  place  because  arterial 
blood  has  a high  affinity  for  the  tissues,  and  venous  blood 
little  or  none.  The  pulmonary  circulation  takes  place  be- 
cause venous  blood  has  a high  affinity  for  atmospheric  oxy- 
gen, which  it  finds  on  the  air  cells  of  the  lungs,  and  arte- 
rial blood  little  or  none.  On  the  same  principle  we  may 
explain  the  rise  of  sap  in  trees,  the  circulatory  movements 
in  the  different  animal  tribes,  and  the  minor  circulations  of 
the  human  system. 

The  most  striking  peculiarity  of  the  blood  is  the  incessant 


What  reasons  are  there  for  supposing  that  the  action  of  the  heart  is  not 
the  only  cause  of  the  circulation  ? What  explanation  may  be  given  of  the 
circulation  in  the  capillaries  ? What  is  the  Cause  of  the  systemic  circula- 
tion ? What  of  the  pulmonary  ? 


CIRCULATION  OF  THE  BLOOD, 


399 


change  which  it  undergoes.  It  is  constantly  being  destroy- 
ed, and  as  constantly  being  reproduced.  It  consists  of  two 
portions,  the  Plasma,  a clear  fluid,  of  a yellowish  tinge, 
which  contains  fibrin,  albumen,  and  fat ; and  in  this  there 
float  disk-like  bodies  of  different  shapes  and  magnitudes  in 
different  animals.  In  man  they  are  about  xoVo^^ 
inch  in  diameter,  consist  of  a sac  of  Globulin,  a body  of  the 
protein  family,  and  in  the  interior  they  contain  a red  sub- 
stance, Hcematin,  which  gives  them  their  peculiar  color. 
On  one  portion  of  them  there  is  a nucleus  or  speck,  consist- 
ing of  coagulated  fibrin.  When  the  disks  are  old  and  about 
to  be  destroyed,  their  interior  is  filled  with  Hcemajphein,  a 
yellow  substance,  corresponding  to  the  coloring  matter  of 
the  urine.  Besides  these,  there  are  lymph,  chyle,  and  oil 
globules  in  the  blood. 

A continuous  metamorphosis  goes  on  during  the  circula- 
tion of  the  blood  ; the  plasma  serves  for  the  purposes  of  nu- 
trition, the  disks  for  the  production  of  heat.  They  absorb 
oxygen  in  the  air  cells  of  the  lungs,  and  transmit  it  to  all 
parts  of  the  system ; and  as  they  grow  old  and  disappear, 
new  ones  are  formed  from  the  plasma. 

Although  fibrin  is  know^n  to  exist  in  plants,  I doubt  very 
much  whether  it  is  directly  absorbed  as  Fibrin  into  the 
system.  Besides  the  direct  proof  which  we  have  from  the 
analysis  of  these  bodies,  we  know  that  fibrin  and  albumen 
so  closely  resemble  each  other  in  constitution  that  they  are 
mutually  convertible  into  each  other.  During  the  hatch- 
ing of  an  egg  from  its  albumen  the  flesh  (fibrin)  of  the 
young  chicken  is  formed,  a phenomenon  accompanying  the 
absorption  of  oxygen  from  the  air.  In  the  human  system, 
abundant  observation  has  proved  that  there  is  a direct  con- 
nection between  the  quantity  of  oxygen  introduced  through 
the  lungs  and  the  amount  of  fibrin  in  the  blood.  When  the 
respiratory  process  is  unduly  active,  the  disks  oxydize  with 
rapidity,  and  the  amount  of  fibrin  increases  ; but  when  the 
reverse  takes  place,  there  is  a restraint  on  the  change  of  the 
disks,  and  the  amount  of  fibrin  declines. 

The  coagulation  of  the  blood  is  a phenomenon  which  has 
excited  much  attention,  physiologists  generally  looking  upon 

Of  what  parts  is  the  blood  composed?  What  are  the  properties  of  the 
plasma  ? Of  what  are  the  disks  composed  ? What  are  globulin,  haematin, 
and  haemaphein  ? What  are  the  functions  of  the  plasma  and  disks  respect- 
ively ? What  reasons  are  there  for  supposing  that  fibrin  may  be  made  in 
the  system  from  albumen  or  casein  ? 


400 


COAGULATION  OF  THE  BLOOD. 


it  either  as  wholly  inexplicable,  or  what,  in  reality,  amounts 
to  the  same  thing,  as  due  to  the  death  of  the  blood.  What 
connection  there  is  between  its  life  and  fluidity,  is  not  so 
very  apparent.  A little  reflection  will,  I am  persuaded, 
deprive  this  phenomenon  of  much  of  its  fictitious  importance, 
since  it  is  plain  that  the  coagulation  .of  the  blood,  or,  in 
other  words,  the  separation  of  fibrin  from  it  takes  place  in 
the  body  as  well  as  out  of  it,  for  from  this  coagulated  fibrin 
the  muscular  tissues  are  formed,  and  from  it  their  waste  is 
repaired.  By  passing  through  two  capillary  circulations, 
the  systemic  and  the  pulmonary,  the  rapidity  of  the  process 
is  very  much  interfered  with  ; but  still,  it  eventually  takes 
place. 

I here  insert  one  of  Lecanu’s  analyses  of  the  blood ; it 
may  serve  to  give  an  idea  of  the  constitution  of  that  liquid. 
It  must  not  be  forgotten,  however,  that  such  analyses,  be- 
yond mere  general  results,  are  of  little  value  ; the  composi- 
tion of  the  blood  varies  incessantly  in  the  same  individual. 
For  instance,  the  mere  accident  of  his  being  thirsty,  or  hav- 
ing recently  drank  abundantly  of  water,  will  make  an  entire 
change  in  the  analysis  of. the  blood. 


Water 780-145. 

Fibrin . 2-100. 

Coloring  matter 133  000. 

Albumen 65-090. 

Crystalline  fatty  matter 2-430. 

Oily  matter  . 1-310. 

Extractive  matter 1-790. 

Salts  and  loss 149-35. 


1000-000. 

The  following  represents  the  constitution  of  hsematosin  : 

Carbon  66-49. 

Hydrogen 530. 

Nitrogen 10-50. 

Oxygen 11 0.5. 

Iron 6'66. 


100-00. 


Does  the  coagulation  of  the  blood  take  place  during  life  ? Of  what  are 
the  muscular  tissues  composed  ? What  circumstances  tend  to  change  the 
constitution  of  the  blood  ? 


PROCESSES  OF  SECRETION. 


401 


LECTURE  XC. 

Nature  of  the  Processes  of  Secretion. — Origin  of 
Secretions. — Phenomena  of  Respiration. — Arterializa- 
tion. — Production  of  Animal  Heat. — Removal  of  effete 
Mattel's. — Constitution  of  Milk. — Uses  of  that  Secre- 
tion. — Mucus.  — Pus.  — Bile.  — Urine.  — Calculi.  — 
Bones. — Nervous  Matter. 

During  the  starvation  of  an  animal  all  its  various  secre- 
tions are  still  formed  ; a consideration  which  proves  that 
the  production  of  urine,  bile,  and  other  such  bodies  is,  in  re- 
ality, connected  with  the  destructive  processes  going  on  in 
the  animal  system.  These  processes  of  decay  originate  in 
the  action  of  oxygen  admitted  by  the  process  of  respiration. 

The  lungs,  which  constitute  the  organ  by  which  air  is 
introduced,  are  originally  developed  as  diverticula  from  the 
oesophagus,  and  finally  become  an  immense  congeries  of 
cells  emptying  into  the  trachea.  In  respiration  they  are 
perfectly  passive,  the  air  being  introduced  and  expelled  al- 
ternately by  muscular  contraction.  It  is  commonly  esti- 
mated that,  on  an  average,  about  17  inspirations  are  made 
each  minute,  and  at  each  inspiration  about  17  cubic  inches 
of  air  are  introduced. 

The  blood  presents  itself  on  the  air  cells  of  a deep  blue 
color,  and  is  then  known  as  venous  blood.  Through  the 
thin  wall  of  the  cell  it  obtains  oxygen  from  the  air,  and 
gives  out  carbonic  acid.  It  is  the  coloring  matter  of  the 
disks  which  discharges  this  function,  and  during  the  act  of 
change  its  tint  alters  to  a bright  crimson.  It  is  said  now 
to  be  arterialized,  or  to  constitute  arterial  blood.  The  mag- 
nitude of  the  scale  on  which  this  operation  is  carried  for- 
ward may  be  appreciated  from  the  circumstance  that  in  a 
man  of  average  size,  in  a single  day,  about  seven  tons  of 
blood  have  been  exposed  to  226  cubic  feet  of  atmospheric  air. 
The  oxygen  thus  introduced  acts  directly  either  on  the  tis- 

How  is  it  known  that  the  secretions  arise  from  destructive  processes  ? 
What  is  the  structure  of  the  lungs  ? How  many  inspirations  does  a man 
make,  on  an  average,  in  a minute  I How  many  cubic  inches  of  air  are  in- 
troduced at  each  inspiration  ? What  is  meant  by  the  arterialization  of  tho 
blood?  What  action  does. the  oxygen  introduced  exert? 


402  NUTRITION  OP  MILK. 

• 

sues  themselves,  as  it  is  distributed  by  the  systemic  circula- 
tion, or  on  the  elements  of  respiration  they  contain.  In  the 
latter  case,  carbonic  acid  gas  and  water  are  the  result ; in 
the  former,  carbonic  acid,  water,  and  ammonia.  But  these 
changes  can  not  take  place  without  an  elevation  of  temper- 
ature. Carbon  and  hydrogen  can  neither  burn  in  the  air 
nor  in  the  animal  system  without  evolving  heat.  The  high 
temperature  which  an  animal  can  maintain  is  therefore  di- 
rectly proportional  to  the  quantity  of  oxygen  it  consumes. 

The  tissues  being  thus  acted  upon,  give  rise,  during  their 
metamorphoses,  to  new  products,  which  require  to  be  re- 
moved from  the  system  ; these,  passing  under  the  name  of 
secretions,  are  discharged  by  glands  or  other  special  organs. 
Thus  the  carbonic  acid,  for  the  most  part,  escapes  from 
the  lungs  ; the  ammonia  through  the  kidneys ; the  water 
through  both  those  organs  and  the  skin.  Liebig  has  at- 
tempted to  show  that  if  the  elements  of  urine  be  added  to 
the  elements  of  bile,  they  will  represent  the  elements  in  the 
blood  ; and  there  can  be  no  doubt  that  the  sulphates  and 
phosphates  found  in  the  urine  arise  directly  from  the  sul- 
phur and  phosphorus  previously  existing  in  the  muscular 
fibre  and  nervous  matter. 

As  an  illustration  of  the  principles  here  given  in  relation 
to  the  functions  of  nutrition  and  secretion,  the  constitution 
and  properties  of  milk  may  be  cited.  The  following  is  an 
analysis  of  it : 


Water 873.00. 

Butter  .....  ‘ 30  00. 

Casein 48*20. 

Milk  sugar 43*90. 


Phosphate  of  lime 2*31. 

“ “ magnesia *42. 

“ “ iron  . *07. 

Chloride  of  potassium 1*44. 

“ “ sodium *24. 

Soda  in  combination  with  casein  . . . *42. 

1000*000. 

Of  the  substances  here  mentioned,  all  are  undoubtedly 
obtained  directly  from  the  food.  In  the  herbage  on  which 
a graminivorous,  milk-giving  animal  feeds,  every  one  of 

In  what  does  animal  heat  arise  ? Through  what  channels  are  the  lead- 
ing secretions,  water,  anunonia,  and  carbonic  acid,  discharged  ? What  sup- 
posed relation  is  there  between  the  constituent  of  the  urine  and  bile  con- 
jointly and  those  of  the  blood?  From  what  do  the  sulphates  and  phos- 
phates of  the  urine  arise  ? What  are  the  chief  constituents  of  milk  ? From 
what  source  are  they  derived  ? 


CHYLE. MUCUS. PUS. BILE. 


403 


these  constituents  occurs.  I have  already  shown  that  the 
butter,  or  fat,  and  the  casein  are  thus  directly  derived,  and 
the  evidence  is  equally  complete  that  all  the  salts  of  phos- 
phoric acid  and  chlorine  arise  from  the  same  source. 

A young  animal,  which,  in  the  first  periods  of  its  life,  is 
nourished  exclusively  on  milk,  finds  in  that  milk  all  the 
various  compounds  it  requires  for  its  own  existence  and 
growth.  The  respiratory  food  is  there — it  is  the  butter  and 
milk  sugar  ; the  nitrogenized  food  is  there — it  is  the  casein  ; 
and  we  have  already  seen  that  albumen  and  casein  are  both 
convertible  into  fibrin  ; the  casein,  thus,  in  the  mother’s 
milk,  becomes  converted  into  flesh  in  the  young  animal. 
To  insure  the  growth  of  its  bones,  phosphate  of  lime  (bone 
earth)  is  present ; there  is  also  chlorine  to  form  the  hydro- 
chloric acid  of  its  gastric  juice,  and  soda,  which  is  an  essen- 
tial ingredient  in  its  bile. 

It  remains  now  to  add  a brief  description  of  the  proper- 
ties of  the  remaining  leading  animal  substances,  among 
which  may  be  mentioned  : 

Chyle  is  usually  of  a white  or  reddish- white  tint.  It  re- 
sembles blood  in  constitution  and  power  of  coagulating.  It 
contains  much  fat,  which  gives  to  it  a cream-like  aspect. 

Mucus  exudes  from  the  surface  of  mucous  membranes. 
It  is  of  a white  or  yellow  color,  of  a viscid  constitution,  and 
insoluble  in  water.  It  dissolves  in  a solution  of  potash,  and 
is  precipitated  by  an  alkali. 

Pus,  a secretion  from  injured  surfaces,  resembling  mucus 
in  many  respects,  but  distinguished  by  not  being  soluble  in 
potash  solution,  but  converted  by  it  into  a gelatinous  body, 
which  can  be  pulled  out  in  threads. 

Bile,  a yellow  liquid,  secreted  by  the  liver  from  the  por- 
tal blood  ; it  turns  green  in  the  air,  has  a bitter  taste  and 
an  alkaline  reaction,  due  to  the  presence  of  soda.  Its  color- 
ing matter  is  chlorophyl.  It  is  regarded  as  a choleate  of 
soda,  the  constitution  of  choleic  acid  bieng  ^16^66^2^22' 
Of  the  correctness  of  this  formula  there  is  considerable 
doubt,  since  it  has  been  recently  affirmed  that  Tauriiie, 
which  is  a derivative  body,  contains  a large  amount  of  sul- 
phur. 

What  becomes  of  the  butter,  milk  sugar,  casein,  phosphate  of  lime,  chlo- 
rine, and  soda  in  the  body  of  the  young  animal  ? What  is  chyle  ? What 
is  mucus  ? How  may  pus  be  distinguished  from  mucus  ? What  are  the 
chief  properties  of  bjle  ? From  what  is  it  formed?  What  does  taurine 
contain  ? 


404 


URINE. NERVOUS  MATTER. 


Urine,  a yellow-colored  fluid,  secreted  by  the  kidneys  ; 
has  an  acid  reaction;  its  specific  gravity  from  1*005  to 
1*030  ; putrefies  at  a moderate  temperature,  its  urea  pass- 
ing into  the  condition  of  carbonate  of  ammonia.  The  chief 
constituents  of  urine  are  urea,  uric  acid,  the  sulphates  and 
phosphates  of  potash,  Soda,  lime,  ammonia,  and  a yellow 
coloring  matter,  with  mucus  of  the  bladder. 

The  constitution  of  the  urine  changes  in  disease.  In  Dia- 
betes  it  contains  grape  sugar,  as  may  be  shown  by  the  test 
of  sulphate  of  copper,  already  mentioned.  Diabetic  urine 
may  even  be  fermented  with  yeast,  and  alcohol  distilled 
from  it. 

Urinary  Calculi  are  stony  concretions  often  formed  in 
the  bladder  of  man  and  many  animals  ; they  are  of  differ- 
ent kinds : 1st.  Uric  acid.  2d.  Urate  of  ammonia.  3d. 
Phosphate  of  lime,  magnesia,  and  ammonia.  4th.  Oxalate 
of  lime,  or  mulberry  calculus.  5th.  Cystic  and  xanthic 
oxides. 

Bones  consist  of  two  parts,  an  animal  and  an  earthy 
matter.  The  latter  is  the  phosphate  of  lime  (bone  earth). 

Nervous  Matter  consists  of  an  albuminous  substance 
with  several  fatty  principles,  distinguished  by  the  remark- 
able fact  that  they  contain  phosphorus.  In  addition,  it 
contains  cholesterine. 

It  would  not  agree  with  the  object  of  these  Lectures 
were  I here  to  offer  any  detailed  remarks  on  the  functions 
of  the  brain  and  the  nervous  system.  Of  the  action  of  the 
lungs,  the  liver,  the  kidneys,  or  other  such  organs,  we  are 
beginning  to  have  a very  distinct  idea  ; but  it  is  altogether 
different  with  the  functions  of  the  cerebro-spinal  axis  ; there 
every  thing  is  in  mystery  and  darkness  ; yet  it  is  in  what 
may  be  hereafter  discovered  in  relation  to  the  action  of  this 
system  that  our  chief  hopes  of  the  advance  of  animal  chem- 
istry and  physiology  depend. 

WTiat  are  the  chief  constituents  of  urine  ? How  may  sugar  be  detected 
in  diabetic  urine  ? What  varieties  of  urinary  calculi  are  there  ? Of  what 
are  bones  composed  ? What  are  the  chief  constituents  of  nervous  matter  ? 


INDEX. 


A. 

Absolute  alcohol,  329. 

Acetal,  338. 

Acetification,  339. 

Acetone,  341. 

Acetyle  compounds,  337. 

Acid,  acetic,  339. 

aconitic,  or  equisetic,  371. 
aldehydic,  338. 
alloxanic,  366. 
amygdalinic,  359. 
anilic,  or  indigotic,  379. 
anthranilic,  380. 
antimonic,  301. 
antimonious,  391. 
apocrenic,  389. 
arsenic,  299. 
arsenious,  296. 

tests  for,  296. 
benzoic,  350. 
boracic,  254. 
butyric,  328. 
capric  and  caproic,  384. 
carbolic,  388. 
carbonic,  249. 

liquefaction  of,  250. 
chloracetic,  341. 
chloric,  238. 
chlorous,  238. 
chlorovalerisic,  350. 
chromic,  293. 
chrysammic,  380. 
chrysanilic,  380. 
cinnamic,  355. 
citric,  370. 
comenic,  375. 
crenic,  389. 
croconic,  325. 
cyanic,  360. 
cyanuric,  360. 
dialuric,  36?. 
elaidic,  384. 
ellagic,  372. 
ethalic,  384. 
ethionic,  337. 
ferric,  287. 
formic,  346. 
fulminic,  360. 
fumaric,  371. 
gallic,  372. 


Acid,  glucic,  323. 
hippuric,  353. 
hydriodic,  244. 
hydrochloric,  239. 
hydrocyanic,  357, 
hydroferrocyanic,  362. 
hydrofluoric,  246. 
hydroflu  os  ilicic,  256. 
hydrosalicylic,  354. 
hydrosulphocyanic,  36i 
hydrosulphuric,  228. 
hyperchloric,  238. 
hyperchlorous,  238. 
hypermanganic,  283. 
hyponitrous,  216. 
hyposulphuric,  227. 
hyposulphurous,  227* 
igasuric,  376. 
isatinic,  380. 
isethionic,  337. 
japonic,  372. 
kinic,  376. 
lactic,  330. 
lithic,  365. 
maleic,  371. 
malic,  371. 
manganic,  282. 
margaric,  383. 
meconic,  374. 
melanic,  355. 
melasinic,  323. 
mesoxalic,  366. 
metagallic,  372. 
metaphosphoric,  233. 
mucic,  325. 
muriatic,  239. 
mykomelinic,  366. 
myristic,  384. 
nitric,  218. 
nitromuriatic,  242. 
nitrous,  216. 
cenanthic,  333. 
oleic,  383. 
oxalic,  323. 
oxalhydric,  325. 
oxaluric,  367. 
palmitic,  384. 
parabanic,  366. 
pectic,  321. 
phosphoric,  232.* 


406 


INDEX. 


Acid,  phosphorous,  232. 
phosphovinic,  334. 
picric,  or  carbazotic,  379. 
pinic,  sylvic  and  pimaric,  386. 
purpuric,  368. 
pyrogallic,  372. 
pyroligneous,  339. 
pyromeconic,  375. 
pyrophosphoric,  233. 
pyrotartaric,  370. 
racemic,  370. 
rhodizonic,  325. 
rubinic,  372. 
saccharic,  325. 
sacchulmic,  322. 
salicylic,  354. 
sebacic,  384. 
silicic,  255. 
stearic,  383. 
suberic,  384. 
succinic,  384. 
sulphamilic,  349. 
sulphindigolic,  379. 
sulphobenzoic,  351. 
sulphoglyceric,  383. 
sulphomethylic,  346. 
sulphonaphthalic,  388. 
sulphosaccharic,  322. 
sulphovinic,  334. 
sulphuric,  225. 
sulphurous,  223. 
tannic,  371. 
tartaric,  369. 
thionuric,  367. 
ulmic,  322,  388. 
uramilic,  367. 
uric,  365. 
valerianic,  349. 
xanthic,  343. 

Acids,  coupled,  369. 

Aconitine,  376. 

Affinity,  cKemical,  173. 

Albumen,  395. 

vegetable,  395. 

Alcargen,  344. 

Alcohol,  329. 

Aldehyde,  337. 

Alizarine,  378. 

Alkarsin,  344. 

Allantoin,  366. 

Alloxan,  366. 

Alloxantine,  367. 

Alumina,  279. 

sulphates,  281. 

Aluminum,  279. 

Alums,  281. 

Amalgamation  process,  307. 

Amalgams,  311. 

Amidine,  319. 

Amidogen,  256. 


Amilen,  349. 

Ammeline  and  ammelide,  364. 
Ammonia,  carbonate,  356. 
nitrate,  356. 

preparation  and  properties 
of,  257,  356. 

sulphate,  357.  * 

Ammoniacal  amalgam,  258,  356. 
Ammonium,  258. 

chloride,  356. 
sulplurets,  259. 
Amygdaline,  359. 

Amyle  compounds,  348. 

Anatto,  378. 

Aniline,  373,  377,  379. 

Animal  chemistry,  389. 

Anthracite,  247. 

Antearine,  376. 

Antimony,  300. 

chloride,  301. 
oxide,  301. 

, sulphurets,  301. 

Aqua  regia,  242. 

Arabine,  321. 

Argol,  329. 

Aricine,  375. 

Arrow-root,  319. 

Arsenic,  295. 

sulphurets,  300. 
Arterialization,  401. 

Arterial  membrane,  397. 
Atmosphere,  composition  of,  200. 

physical  constitution  of, 
199. 

Atmospheric  pressure,  201. 

Atomic  weights,  154. 

Atoms,  5. 

Atropine,  376. 

Aurum  musivum,  292. 

Azote,  198. 

B. 

Balloons,  16.  ^ 

Balsams,  386. 

Barium,  272. 

chloride,  273. 
oxides,  272. 
sulphuret,  273. 

Barley  sugar,  320. 

Barometer,  208. 

Baryta,  273. 

carbonate,  273. 
sulphate,  274. 

Bassorine,  321. 

Batteries,  voltaic,  l!57. 

Bell  metal,  304. 

Benzamide,  351. 

Benzine,  352. 

Benzoine,  352. 

Benzone,  352. 


INDEX. 


407 


Benzyle  compounds,  350. 

Bile,  403. 

Biscuit  ware,  280. 

Bismuth,  306. 

nitrates,  306. 
oxides,  306. 

Bleaching  powder,  277. 

Blood,  composition  of,  400. 

Boiling  points  of  fluids,  50. 

Bone  earth,  277. 

Bones,  composition  of,  404. 

Boron,  254. 

Brain,  composition  of,  404. 

Brass,  304. 

British  gum,  320. 

Bromine,  preparation  and  properties 
of,  245. 

Brucia,  376. 

Buffy  coat,  396. 

Butyrine,  384. 

C. 

Cadmium,  291. 

compounds  of,  291. 
Caffeine,  376. 

Calamine,  electric,  290. 

Calcium,  275. 

chloride,  276. 
fluoride,  276. 
sulphurets  of,  276. 

Calculi,  urinary,  404. 

Calomel,  310. 

Calorimeter,  31. 

Camphor,  385. 

artificial,  385. 

Caoutchouc,  386. 

Capacity  for  heat,  29. 

Caramel,  320. 

Carbon,  246. 

chlorides  of,  336. 
its  compounds  with  oxygen, 
248. 

sulphuret  of,  253. 

Carbonic  oxide,  preparation  and  prop- 
erties of,  248. 

Carbyle,  sulphate  of,  336. 

Carmine,  380. 

Carthamine,  378. 

Casein,  395,  396. 

vegetable,  395. 

Cassava,  319. 

Cast  iron,  284. 

Catechin  and  catechu,  372. 

Cedriret,  387. 

Cellulose,  321. 

Cerine,  384. 

Cerium,  281. 

Chameleon,  mineral,  282,  283. 
Charcoal,  properties  of,  247. 
Chinoidine,  376. 


Chloral,  342. 

Chloric  acid,  238. 

Chlorine,  235. 

compounds  with  oxygen, 
237. 

preparation  and  propertied 
of,  235. 

Chlorisatine,  380. 

Chlorocinnose,  355. 

Chloroform,  347. 

Chlorophyll,  378. 

Chlorosamide,  354. 

Chlorureted  acetic  ether,  342. 

formic  ether,  342. 
Chlorous  acid,  238. 

Cholesterine,  384. 

Chondrin,  397. 

Chrome  yellow,  294. 

Chromic  acid,  salts  of,  294. 

oxide,  salts  of,  294. 
Chromium,  293. 

oxide,  293. 

Chyle,  391,  403. 

Chyme,  391. 

Cinchona,  375. 

Cinnabar,  310. 

Cinnamyle  compounds,  355. 
Circulation  of  blood,  398. 

Clays,  composition  of,  279. 

Clay  iron  stone,  284. 

Coagulation,  399. 

Coal,  389. 

oil,  388. 

Cobalt,  289. 

characters  of  salts  of,  289. 
chloride,  289. 
oxalate,  289. 
oxides,  289. 
Cobaltocyanogen,  363. 

Cocoa  tallow,  384. 

Codeine,  374. 

Cohesion,  7. 

Colchicine,  376. 

Cold  rays,  74. 

Colophony,  386. 

Coloring  principles,  377. 

Colors,  88. 

Columbium,  295. 

Combination,  by  volumes,  163. 

laws  of,  160. 
Combining  numbers,  160. 

table  of,  154. 

Combustion,  183. 

Compound  radicals,  316. 
Condensation  of  vapors,  49. 
Conicine,  or  conia,  376. 

Copper,  302. 

alloys  of,  304. 
arsenite,  304. 
carbonates,  303. 


408 


INDEX. 


Copper,  nitrate,  304. 
oxides,  303. 
sulphate,  303. 

Corrosive  sublimate,  310. 

Creasote,  387. 

Cryophorus,  53. 

Crystallization;  crystallography,  165. 
Cupellation,  307. 

Curarine,  376. 

Cyamelide,  360. 

Cyanides,  metallic,  359,  360. 
Cyanogen,  253,  357. 

chlorides  of,  361. 

Cystic  oxide,  368. 

D. 

Daguerreotype,  101. 

Dammara  resin,  386. 

Daphnine,  376. 

Daturine,  376. 

Decomposition  of  water,  131. 
Delphinine,  376. 

Deutoxide  of  nitrogen,  215. 

Dew,  74^ 

Dew-point,  56. 

Dextrine,  319. 

Diamond,  247. 

Diastase,  319. 

Differential  thermometer,  18. 
Diffusion  of  gases,  211. 

Digestion,  392. 

Dimorphism,  169. 

Dispersion,  81. 

Dragon’s  blood,  386. 

Dross,  305. 

Dutch  liquid,  335. 

E. 

Earthen-ware,  manufacture  of,  280. 
Ebullition,  48. 

Elaidine,  384. 

Elaldehyde,  338. 

Elaterine,  376. 

Electricity,  action  of,  on  the  magnet, 
141. 

animal,  151. 
conduction  of,  107. 
of  steam,  152. 
statical,  105. 
voltaic,  123. 
Electro-chemistry,  133. 

Electrolysis,  134. 

Electrometers,  119.  ^ 

Electrotype,  137. 

Electrophorus,  122. 

Emetine,  376. 

Emulsine,  359. 

Enamel,  292. 

Equivalent  numbers,  154. 

Equivalent  numbers,  table  of,  154. 


Eremacausis,  317. 

Essences,  384. 

Ethal,  384. 

Ether,  331. 

continuous  process  for,  335. 
Ethers,  compound,  332. 

Ether,  heavy  muriatic,  342. 

Etherole  and  etherine,  336. 

Ethyle  group,  332. 

Eudiometer,  Ure’s,  199. 

Eupione,  387. 

Evaporation,  60. 

at  low  temperatures, 
60. 

Expansion  of  solids,  23. 

fluids,  18. 
gases,  15. 

F. 

Faraday’s  theory  of  polarization,  121. 
Fatty  bodies,  38b. 

Fermentation,  alcoholic,  326. 

- lactic,  328,  330. 
Ferridcyanogen  compounds,  363. 
Ferrocyanogen  compounds,  362. 
Fibrin,  395. 

vegetable,  395. 

Fixed  air,  249. 

Flame,  structure  of,  186. 

Fluoride  of  boron,  255. 

Fluorine,  245. 

Formomethylal,  347. 

Freezing  of  water  by  evaporation,  54. 
Freezing  mixtures,  40. 

Fusel  oil,  348. 

Fusible  metal,  307. 

G. 

Galvanism,  124. 

Galvanometer,  143. 

Gambogo,  378. 

Gay-Lussac’s  law,  213. 

Gelatin,  396. 

Gentianine,  376. 

Geoffrey’s  tables,  176. 

Glass,  manufacture  of,  280. 

soluble,  281. 

Globulin,  399. 

Glucinum,  281. 

Glucose,  320. 

Glycerine,  382,  383. 

Gold,  311. 

compounds  of,  311. 
Goniometers,  168. 

Goulard’s  water,  340. 

Graphite,  247. 

Gravity,  specific,  of  gases,  determin- 
ation of,  164. 

Green,  Scheele’s,  304. 

Grove’s  battery,  130. 


INDEX. 


409 


Gum,  British,  320. 

Arabic — tragacanth,  321. 

Gun  cotton,  325. 

Gunpowder,  267,  268. 

Gypsum,  277. 

H. 

Haemaphein,  399. 

Haematin,  399. 

Haematite,  284. 

Haematoxyline,  378. 

Hair,  397. 

Hare’s  batteries,  129,  138. 

blow-pipe,  191. 

Heat,  animal,  402. 

capacity  for,  29. 
conduction  of,  61. 
exchanges  of,  72. 
latent,  39. 

radiation,  ^reflection,  absorp- 
tion, and  transmission  of,  67. 
varieties  of,  71. 

Hesperidine,  376. 

Horn,  397. 

Hydrobenzamide,  351. 

Hydrogen,  antimoniureted,  302. 
arseniureted,  300. 
light  carbureted,  251. 
peroxide  of,  197. 
persulphuret  of,  230. 
phosphureted,  234. 
preparation  and  proper- 
ties of,  187. 
sulphureted,  228. 
Hygrometer,  Daniell’s,  56. 
Hygrometiy,  55. 

Hyoscyamine,  376. 

Hyponitrous  acid,  216. 
Hyposulphurous  acid,  227. 

I. 

Ideal  coloration,  102. 

Iclrialine,  389. 

Indigo,  378. 

Induction,  110. 

Interference,  88. 

Interstices,  6. 

Inuline,  319. 

Iodine,  preparation  and  properties 
of,  242. 

Iridium,  313. 

Iron,  283. 

, carbonate,  288. 

cast,  varieties  of,  284. 
characters  of  salts  of,  286. 
chlorides,  287. 
manufacture,  284. 
oxides  of,  286. 
passive,  285. 
sulphates,  288. 

s 


Iron,  sulphurets,  288. 

Isatine,  379. 

Isomerism,  171. 

Isomorphism,  170. 

K. 

Kakodyle  and  its  compounds,  343. 

Kapnomar,  387. 

Kermes  mineral,  301. 

Kyanol,  388. 

L. 

Lac,  386. 

Lactine,  321. 

Lampblack,  247. 

Lamps,  safety,  63. 

Lantnanium,  281. 

Latent  heat,  39. 

Laughing  gas,  214. 

Laws  of  combination,  160. 

Lead,  304. 

action  of  water  on,  305. 
alloys  of,  306. 
carbonate,  306. 
characters  of  salts  of,  306. 
chloride,  305. 
iodide,  305. 
nitrate,  306. 
oxides,  305. 

Leaven,  326. 

Lecanorine,  380. 

Leiocome,  320. 

Leukol,  377. 

Leyden  jar,  116. 

Light,  cause  of,  75. 

chemical  action  of,  83. 
reflection,  refraction,  and  po- 
larization of,  92-94. 
wave  theory,  76,  83. 

Lignine,  321. 

Lignite,  389. 

Lime,  275. 

carbonate,  276. 
chloride,  276. 
phosphate,  277. 
salts,  characters  of,  276. 
sulphate,  277. 

Liquor  of  Libavius,  292. 

Lithium,  272. 

Litmus,  380. 

xM. 

Madder,  378. 

Magnesia,  277. 

carbonate,  278. 
characters  of  salts  of,  278. 
phosphate,  278. 
sulphate,  278. 

Magnesium,  preparation  and  proper- 
ties of,  277. 


410 


INDEX. 


Magnetism,  141. 

Magnets,  artificial,  146. 
Magneto-electricity,  147. 
Malachite,N303. 

Manganese,  characters  of  salts  of, 
282. 

chloride,  283. 
oxides  of,  282. 
preparation  and  proper- 
ties of,  282. 
sulphate,  283, 
Margarine,  382,  383. 

Margarone,  383. 

Marriotte,  law  of,  46,  212. 

Marsh’s  test  for  arsenic,  298. 
Maximum  density,  22. 

Meconine,  374,  376. 

Medicated  waters,  384. 

Melam  and  melamine,  364. 

Mellone,  364. 

Mercaptan,  342. 

Mercury,  309. 

characters  of  salts  of,  310. 
chlorides,  310. 
iodides,  310. 
nitrates,  310. 
oxides  of,  309. 
sulphates,  310. 
sulphurets,  310. 

Mesityle,  342. 

Metaldehyde,  338. 

Metal,  fusible,  307. 

Metals,  general  properties  of,  260. 

classification  of,  261. 
Methyle  compounds,  345. 
Microcosmic  salt,  272. 

Milk,  composition  of,  402. 
Mindererus  spirit,  340. 

Mineral  chameleon,  282,  283. 
Molybdenum,  295. 

Mordants,  280. 

Morphia,  374. 

Mosaic  gold,  292. 

Mucilage,  321. 

Mucus,  403. 

Multipliers,  143. 

Murexan,  368. 

Murexide,  367. 

Muscovado  sugar,  320. 

Myricine,  384. 

N. 

Naphtha,  388,  389. 

Naphthaline,  388. 

Narceine,  374. 

Narcotine,  374. 

Nervous  substance,  404. 

Nickel,  288. 

sulphate,  288. 

Nihil  album,  290. 


Nitric  acid,  218. 

Nitrobenzide,  353. 

Nitrogen,  chloride  of,  239. 

its  compounds  with  oxy- 
gen, 198. 

preparations  and  proper- 
ties of,  197, 

Nitrous  acid,  216. 

oxide,  214. 

Nomenclature,  153. 

Nutmeg  butter,  384. 

Nutrition,  function  of,  397. 

O. 

OEnanthic  ether,  333. 

Ohm’s  theory,  139. 

Oils  and  fats,  381. 

Oil  of  bitter  almonds,  350. 
cajeput,  385. 
cinnamon,  355. 
copaiva,  385. 
horseradish,  385. 
lavender,  385. 
lemons,  385. 
mustard,  385. 
peppermint,  385. 
rosemary,  385. 
spiraea,  354. 
storax,  385. 
turpentine,  385. 
vitriol,  preparation  of,  225. 
wine,  heavy,  336. 

Oils,  palm  and  cocoa,  383,  384. 
volatile,  384. 

Oleine,  382,  383. 

Olefiant  gas,  252. 

Orcine,  orceine,  380. 

Organic  bodies,  classification  of,  318. 

decomposition  of,  by 
heat,  315. 

general  characters 
of,  314. 

chemistry,  314. 

Orpiment,  300. 

Osmium,  295. 

Oxalates,  324. 

Oxamethane,  333. 

Oxamide,  24,  333. 

Oxygen,  preparation  and  properties 
of,  179. 

Ozocherit,  389. 

P. 

Palladium,  311. 

Palmitine,  383. 

Palm  oil,  383. 

Papin’s  digester,  49. 

Paracyanogen,  357. 

Paraffine,  387. 

Paranaphthaliiie,  388. 


INDEX. 


411 


Paschal’s  experiment,  209. 

Pectine,  321. 

Perchloric  acid,  238. 

Petroleum,  389. 

Pewter,  293. 

Phloridzine,  376. 

Phosphorescence,  83,  103. 
Phosphoric  acid,  232. 

Phosphorus,  compounds  with  oxy- 
gen, 231. 

preparation  and  prop- 
erties of,  230. 
Phosphureted  hydrogen,  234. 
Photography,  101. 

Picamar,  387. 

Picrotoxine,  376. 

Pile,  voltaic,  128. 

Piperine,  376. 

Pitch,  387. 

Pit-coal,  389. 

Pittakal,  387. 

Plasma,  399. 

Platinum,  312. 

black,  312. 
chlorides,  313. 
oxides,  313. 

power  of  determining  un- 
ion of  gases,  312. 
salts,  combustible,  377. 
spongy,  312. 

Plumbago,  or  graphite,  247. 
Polarization  of  light,  92. 

Populine,  376. 

Porcelain,  manufacture  of,  280. 
Potassium,  chloride  of,  267. 

iodide  of,  267. 
peroxide  of,  265. 
preparation  and  proper- 
ties of,  264. 
sulphurets  of,  267. 
Potash,  265. 

bicarbonate,  267. 
bisulphate,  267. 
carbonate,  267. 
chlorate,  268. 
hydrate  of,  265. 
nitrate,  267. 
salts,  test  for,  266. 
sulphate,  267. 

Potato  oil  and  its  compounds,  348. 
Prism,  80. 

Protein,  396. 

Prussian  blue,  362. 

Pseudomorphine,  374. 

Purple  of  Cassius,  292,  311. 

Pus,  403. 

Putty  powder,  S9S. 

Pyroacetic  spirit,  341. 

Pyrometer,  24. 

Daniell’s,  28. 


Pyroxylic  spirit,  345. 

Q. 

Quercitron  bark,  378. 

Quicksilver,  309. 

Quina,  375. 

Quinoline,  377. 

R. 

Radiation,  67. 

Rays  of  the  sun,  chemical,  100. 
Realgar,  300. 

Reflection,  law  of,  94. 

Refraction,  law  of,  80,  94. 

Resins,  385. 

Respiration,  185. 

Rhodium,  313. 

S. 

Sacchulmine,  322. 

Safety  jet,  Plemming’s,  63. 

Safety  lamp,  63. 

Sago,  319. 

Salicine,  353,  376. 

Salicyle  compounds,  354. 

Seheele’s  green,  304. 

Secretion,  401. 

Selenium,  230. 

Silicon,  255. 

Silver,  307. 

ammoniuret,  309. 
characters  of  salts  of,  308. 
chloride,  308. 

German,  289. 
iodide,  308. 
nitrate,  308. 
oxides,  308. 
sulphuret,  308. 

Smalt,  289. 

Soaps ; saponification,  382. 

Soda,  biborate,  272. 

bicarbonate,  270. 
carbonate,  370. 
hydrate  of,  271. 
nitrate,  271. 
phosphates  of,  271. 
sulphate,  271. 

Soda  water,  250. 

Sodium,  chloride,  269. 

preparation  and  properties 
of,  268. 

Solanine,  376. 

Solder,  293. 

Specific  gravity,  164. 

heat,  29. 

Spectres,  103. 

Spectrum,  solar,  81-83. 

Speculum  metal,  304. 

Spermaceti,  384. 

Spiraea  ulmaria,  oil  of,  354. 

Starch,  318. 


412 


INDEX. 


Steam,  elastic  force  of,  53. 

engine,  49,  59. 

Stearine,  382. 

Stearopten,  384. 

Steel,  285. 

Stone-ware,  manufacture  of,  280. 
Strontia,  274. 

nitrate,  275. 
sulphate,  275. 

Strontium,  274. 

chloride,  274. 

Strychnia,  376. 

Sublimate,  corrosive,  310. 
Substitution,  317. 

Sugar,  cane,  320. 

eucalyptus,  321. 
from  ergot  of  rye,  321, 
grape,  321. 

of  diabetes  insipidus,  320. 
of  milk,  321. 

Sulphobenzide,  352. 

Sulphocyanogen  compounds,  363. 
Sulphur  compounds  with  oxygen, 
223. 

occurrence  in  nature,  221. 
properties  of,  222. 
Sulphureted  hydrogen,  228, 
Sulphuric  acid,  225. 

Sulphurous  acid,  223. 

Symbols,  156. 

table  of,  154. 

Synaptase,  359. 

Systems,  crystallographical,  165. 

T. 

Tapioca,  319. 

Tar,  varieties  of,  387. 

Tartar,  cream  of,  369. 

Taurine,  403. 

Tellurium,  302. 

Thebaine,  374. 

Theine,  376. 

Theobromine,  376. 
Thermo-electricity,  148. 
Thermometer,  Breguet’s,  34. 

construction  of,  19. 
differential,  18. 
Sanctorio’s,  17. 
scales,  20. 

Thorium,  281. 

Tin,  291. 

chlorides,  292. 
oxides,  292. 
sulphurets,  292. 

Tinned  plate,  293. 

Titanium,  295, 

Transverse  vibrations,  86. 

Tungsten,  295. 


Turmeric,  378. 

Turpeth  mineral,  311. 

Type  metal,  302. 

Types,  chemical,  316. 

U. 

Ulmine,  322,  388. 

Undulatory  theory,  84. 

Uramile,  367. 

Uranium,  302. 

Urea,  361,  365. 

Urinary  calculi,  404. 

Urine,  composition  of,  404, 

V. 

Vanadium,  295. 

Vapor,  elastic  force  of,  52. 

Vapors,  density  of,  58. 
nature  of,  42. 

Vaporization  at  low  temperatures, 
laws  of,  43. 

Vegeto-alkalies,  373. 

Veratria,  376. 

Verdigris,  340,  341. 

Vermilion,  310. 

Vinegar,  339. 

Vitriol,  blue,  303. 

green,  288. 
oil  of,  226. 
white,  290. 

Voltameter,  137. 

Volumes,  combination  by,  163. 

W. 

Water,  composition  of,  134,  192. 

of  crystallization,  196. 
Waves,  length  of,  91. 

Wax,  384. 

Wines,  329. 

Wire  gauze,  62. 

Wood-spirit  and  its  compounds,  345. 

ether,  345. 

Woody  fibre,  321. 

X. 

Xanthic  acid,  343. 

oxide,  368. 

Xyloidine,  325. 

Y. 

Yeast,  327. 

Yttrium,  281. 

Z. 

Zaffre,  289. 

Zinc,  289. 

oxide  of,  290, 
silicate,  290. 
sulphate,  290,. 

Zirconium,  281. 

END. 


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tory, Plans  of  Battles,  Sieges,  <fec.,  and  Historical,  Geograph- 
ical, and  Archieological  Indexes.  Map,  Portrait,  &c.  12mo, 

Sheep  extra,  $1  00. 

The  ,®neid  of  Virgil.  With  English  Notes,  Critical  and  Explana- 
tory, a Metrical  Clavis,  and  an  Historical,  Geographical,  and 
Mythological  Index.  Portrait  and  many  Illustrations.  12mo, 
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Eclogues  and  Georgies  of  Virgil.  With  English  Notes,  Critical  and 
Explanatory.  12mo,  Sheep  extra,  |1  25. 

Sallust’s  Jugurthine  War  and  Conspiracy  of  Catiline.  With  an  En- 
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New  Edition,  corrected  and  enlarged.  Portrait.  12mo,  Sheep 
extra,  75  cents. 

The  Works  of  Horace.  With  English  Notes,  Critical  and  Explana- 
tory. A new  Edition,  corrected  and  enlarged,  with  Excursions 
relative  to  the  Vines  and  Vineyards  of  the  Ancients ; a Life 
of  Horace,  <kc.  12mo,  Sheep  eidra,  $1  25. 

Cicer  Select  Orations.  With  English  Notes,  Critical  and  Explan- 
atory, and  Historical,  Geographical,  and  Legal  Indexes.  Aa 
improved  Edition.  Portrait.  12mo,  Sheep  extra,  $1  00. 


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3 


Anthon’s  Classical  Series,  continued. 

Cicero  de  Senectute,  De  Amicitia,  and  Paradoxa,  and  the  Life  of 
Atticus  by  Nepos.  With  English  Notes,  Critical  and  Explan- 
atory. 12mo,  JSheep  extra,  15  cents. 


Cicero’s  Tusculan  Disputations.  With  English  Notes,  Critical  and 
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The  Germania  and  Agricola,  and  also  Selections  from  the  Annals, 
of  Tacitus.  With  English  Notes,  Critical  and  Explanatory. 
12mo,  Sheep  extra,  $1  00. 

Cornelius  Nepos.  Comelii  Nepotis  Vitae  Imperatorum  Excellentium. 
With  English  Notes,  &c.  12mo,  Sheep  extra,  |1  00. 

Terence.  Terentii  Comoediae,  with  English  Notes,  Metrical  Tables, 
and  an  Essay  on  the  Scanning  of  Terence,  &e.  12mo,  Sheep 

extra.  (In  press.) 

First  Greek  Lessons.  Containing  the  most  important  Parts  of  the 
Grammar  of  the  Greek  Language,  together  with  appropriate 
Exercises  in  the  Translating  and  Writing  of  Greek;  for  the  use 
of  Beginners.  12mo,  Sheep  extra,  75  cents. 


Greek  Prose  Composition.  Greek  Lessons,  Part  II.  An  Introduc- 
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Grammar  of  the  Greek  Language.  For  the  use  of  Schools  and  Col- 
leges. 12mo,  Sheep  extra,  7^  cents. 


A New  Greek  Grammar.  From  the  German  of  Kiihner,  Matthise, 
Buttmann,  Rost,  and  Thiersch;  to  which  are  appended  Re- 
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75  cents. 

Greek  Prosody  and  Metre.  For  the  use  of  Schools  and  Colleges; 
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appended  Remarks  on  the  Indo-Germanic  Analogies.  12mo, 
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A Greek  Reader.  Principally  from  the  German  of  Jacobs.  With 
English  Notes,  Critical  and  Explanatory,  a Metrical  I^d^  to 
Homer  and  Anacreon,  and  a eopious  Lexicon.  12mo,  Sheep 
extra,  $1  00. 


Homer.  The  First  Six  Books  of  Homer’s  Biad,  to  which  are  ap- 
pended English  Notes,  Critical  and  Explanatory,  a MetneaUn- 
dex,  and  Homeric  Glossary.  New  and  enlarged  ion. 
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The  Anabasis  of  Xenophon.  With  English  Notes,  Critical  and  Ex- 
planatory, a Map  arranged  according  to  the  latest  and  , 
thorities,  and  a Plan  of  the  Battle  of  Cunaza.  12mo,  p 
extra,  .1^1  25. 


4 


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Authon’s  Classical  Series,  contiimed. 

Xenophon’s  Elemorabilia  of  Socrates.  Froni  the  Text  of  Kuhner. 
With  Explanatory  Kotes,  &c.,  by  D.  B.  Hickie,  LL.D.  First 
Ameriean  Edition,  corrected  and  enlarged.  12mo,  Sheep  ex- 
tra, $100. 

Manual  of  Roman  Antiquities.  From  the  most  recent  German 
Works.  With  a Description  of  the  City  of  Rome,  &c.  12mo, 

Sheep  extra,  SYi  cents. 

Manual  of  Greek  Literature.  With  a Critical  History  of  the  Greek 
Language.  12mo,  Sheep  extra,  $1  00. 

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Sources.  12mo,  Sheep  extra,  87i  cents. 

Manual  of  Greek  and  Roman  Mythology.  12mo,  Sheep  extra. 

Latin  Syntax.  Latin  Lessons,  Part  II.  Containing  Latin  Sjmtax, 
with  Reading  Lessons,  and  Exercises  in  double  translation,  on 
the  basis  of  Kiihner’s.  12mo,  Sheep  extra.  (Uniform  with 
Latin  Lessons,  Part  I.) 

Ovid.  Selections  from  the  Metamorphoses  of  Ovid.  With  English 
Kotes,  Critical  and  Explanatory.  12mo.  {In  press.) 


Euripides.  The  Hecuba,  Hippolytus,  Medea,  and  Bacchas  of  Eurip- 
ides. AYith  English  Notes,  Critical  and  Explanatory.  12mo. 
{In  press.) 

Juvenal.  The  Satires  of  Juvenal.  AVith  English  Notes,  Critical 
and  Explanatory.  {In  press.) 

Bigelow  on  the  Useful  Arts, 

considered  in  Connection  with  the  Applications  of  Science. 
With  numerous  Engravings.  2 vols.  12mo,  Muslin,  |1  50. 

Boucharlat’s  Mechanics. 

An  Elementary  Treatise  on  Mechanics.  Translated  from  the 
French,  with  Additions  and  Emendations,  by  Prof.  Edward  H. 
Courtenay.  Plates.  8vo,  Sheep  extra,  $2  25. 

Boyd’s  Eclectic  Moral  Phil9Sophy ; 

prepared  for  Literary  Institutions  and  general  Use.  12mo, 
Muslin,  ^75  cents. 

Boyd’s  Rhetoric  and  Criticism. 

Elements  of  Rhetoric  and  Literary  Criticism,  with  copioiis 
Practical  Exercises  and  Examples.  Including,  also,  a succinct 
History  of  the  English  Language,  and  of  British  and  American 
Literature,  from  the  earliest  to  the  present  Times.  On  the 
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with  large  Additions  from  other  Sources.  12mo,  Half  Bound, 
50  cents. 


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5 


Branded  Encyclopedia. 

A Dictionary  of  Science,  Literature,  and  Art;  comprising  the 
History,  Description,  and  Scientific  Principles  of  every  Branch 
of  Human  Knowledge ; with  the  Derivation  and  Definition  of 
all  the  Terms  in  general  use.  Illustrated  by  numerous  En- 
gravings on  Wood.  8 VO,  Sheep  extra,  $4  00. 

Burke  on  tke  Sublime  and  Beautiful. 

Essay  on  the  Sublime  and  Beautiful.  A Philosophical  Inquiry 
into  the  Origin  of  our  Ideas  of  the  Sublime  and  the  Beautiful. 
With  an  Introductory  Discourse  concerning  Taste.  Edited  by 
Abraham  Mills.  12mo,  Muslin,  75  cents. 

Buttmann’s  Greek  Grammar. 

A Greek  Grammar,  for  the  use  of  High  Schools  and  Universi- 
ties. Revised  and  enlarged  by  Alexander  Buttmann.  Trans- 
lated from  the  18th  German  Edition,  by  Edward  Robinson, 
D.D.,  LL.D.  8vo,  Sheep  extra,  $2  00. 

Campbell’s  PbUosopliy  of  Rhetoric. 

Revised  Edition.  12mo,  Muslin,  $1  25. 

Cicero’s  Orator. 

Cicero’s  Three  Dialogues  on  the  Orator.  Translated  into  En- 
glish, by  W.  Guthrie.  Revised  and  Corrected,  with  Kotes. 
18mo,  Muslin,  45  cents. 

Clark’s  Elements  of  Algebra. 

Embracing,  also,  the  Theory  and  Application  of  Logarithms; 
together  with  an  Appendix,  containing  Infinite  Series,  the 
General  Theory  of  Equations,  and  the  most  approved  Methods 
of  resolving  the  higher  Equations.  8vo,  Sheep  extra,  $1  00. 

Comte’s  Philosophy  of  Mathematics. 

Translated  from  the  Cours  de  Philosophie  Positive,  by  W.  M. 
Gillespie,  AM.  8vo,  Muslin,  |1  25. 

Crabb’s  Synonyms. 

English  S3monyms  explained.  With  copious  Illustrations  and 
Explanations,  drawn  from  the  best  Writers.  8vo,  Sheep  ex- 
tra, $2  00. 

Dickens’s  Child’s  History  of  England. 

2 vols.  or  1,  16mo,  Muslin,  |1  00. 

Docharty’s  Arithmetic. 

12mo,  Sheep  extra.  {In  press. ) 

Docharty’s  Institutes  of  Algebra. 

Being  the  First  Part  of  a Course  of  Mathematics,  designed  for 
the  use  of  Schools,  Academies,  and  Colleges.  12mo,  Sheep  ex- 
tra, 75  cents. 

Draper’s  Text-book  on  Chemistry, 

for  the  use  of  Schools  and  Colleges.  Carefully  revised,  with 
Additions.  With  800  Illustrations.  12mOi  Sheep,  75  cents. 


6 


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Draper’s  Text-book  on  Natural  Philosophy, 

lor  the  use  of  Schools  and  Colleges.  Containing  the  most  re- 
cent Discoveries  and  Facts,  compiled  from  the  best  Authorities. 
With  nearly  400  Illustrations.  12mo,  Sheep  extra,  75  cents. 

Draper’s  Chemical  Organization  of  Plants. 

A Treatise  on  the  Forces  which  produce  the  Organization  of 
Plants.  With  an  Appendix,  containing  several  Memoirs  on 
Capillary  Attraction,  Electricity,  and  the  Chemical  Action  of 
Light  Engravings.  4to,  Muslin,  $2  50. 

Duff’s  Book-keeping. 

The  North  American  Accountant : embracing  Single  and  Double 
Entry  Book-keeping,  practically  adapted  to  the  Inland  and 
Maritime  Commerce  of  the  United  States.  Exemplifying  all 
Modern  Improvements  in  the  Science,  with  a new  and  certain 
Method  of  detecting  Errors  and  proving  the  Ledger.  Embrac- 
ing an  improved  Plan  of  Instruction.  Complete  in  Two  Parts. 
8vo,  School  Edition,  Half  Sheep,  7 5 cents ; Mercantile  Edition, 
Muslin,  |1  50. 

Findlay’s  Classical  Atlas, 

to  Illustrate  Ancient  Geography.  Comprised  in  25  Maps, 
showing  the  various  Divisions  of  the  World  as  known  to  the 
Ancients.  With  an  Index  of  the  Ancient  and  Modern  Names. 
8vo,  Half  Bound,  $3  25. 

Fowler’s  English  Language, 

in  its  Elements  and  Forms.  With  a History  of  its  Origin  and 
Development,  and  a full  Grammar.  Designed  for  use  in  Col- 
leges and  Schools.  8vo,  Muslin,  $1  50;  Sheep  extra,  $1  75. 

Goldsmith’s  History  of  Greece. 

Abridged  by  the  Author.  Edited  by  the  Author  of  “ Ameri- 
can Popular  Lessons.”  18mo,  Half  Sheep,  45  cents. 

Goldsmith’s  History  of  Rome. 

Abridged  by  the  Author.  Edited  by  H.  W.  Herbert.  18mo, 
Half  Sheep,  45  cents. 

Gray’s  and  Adams’s  Elements  of  Geology. 

Engravings.  12mo,  Sheep  extra,  75  cents. 

Gray’s  Elements  of  Natural  Philosophy. 

Designed  as  a Text-book  for  Academies,  High  Schools,  and 
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75  cents. 

Griscom’s  Animal  Mechanism 

and  Physiology ; being  a plain  and  familiar  Exposition  of  the 
Structure  and  Functions  of  the  Human  System.  Designed  for 
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7 


Hackley’s  Algebra. 

A Treatise  on  Algebra.  8vo,  Sheep  extra,  $1  60.  A School 
and  College  Edition,  8vo,  Muslin,  $1  00. 

Hackley’s  Oeometry. 

An  Elementary  Course  of  Geometry,  for  the  use  of  Schools  and 
Colleges.  8 VO,  Sheep  extra,  ^75  cents. 

Hale’s  History  of  the  United  States, 

from  their  first  Settlement  as  Colonies  to  the  Close  of  the  Ad- 
ministration of  Mr.  Madison  in  1817.  2 vols.  18mo,  Muslin, 

90  cents. 

Harper’s  Statistical  Gazetteer  of  the  World, 

particularly  describing  the  United  States  of  America,  Canada, 
New  Brunswick,  and  Nova  Scotia.  By  J.  Calvin  Smith.  Il- 
lustrated by  Seven  Maps.  8vo,  $5  00. 

Harper’s  Map  of  the  United  States  and  Canada. 

Showing  the  Canals,  Rail-roads,  and  principal  Stage  Routes. 
By  Samuel  Breese,  A.M.  On  Rollers,  States  traced,  |2  00; 
States  colored,  |2  00 ; States  colored  and  bordered,  $2  25 ; 
Counties  colored,  $2  50. 

Harper’s  New  York  Class-book. 

Comprising  Outlines  of  the  Geography  and  History  of  New 
York ; Biographical  Notices  of  Eminent  Individuals ; Sketches 
of  Scenery  and  Natural  History;  Accounts  of  Public  Institu- 
tions. Arranged  as  a Reading-book  for  Schools.  By  William 
Russell.  12mo,  Sheep  extra,  $1  00. 

Harrison’s  Latin  Grammar. 

An  Exposition  of  some  of  the  Laws  of  the  Latin  Grammar. 
12mo,  Sheep  extra,  75  cents. 

Haswell’s  Engineering. 

Engineers’  and  Mechanics’  Pocket-book,  containing  United 
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of  a Circle;  Squares  and  Cubes,  Square  and  Cube  Roots; 
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terials, Water  Wheels,  Hydraulics,  Hydrostatics,  Pneumatics, 
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Water,  Gunpowder,  Cables  and  Anchors,  Fuel,  Air,  Guns,  <fec., 
&c.  Tables  of  the  Weights  of  Metals,  Pipes,  <fec.  Miscellane- 
ous Notes,  Dimensions  of  Steamers,  Mills,  Motion  of  Bodies  in 
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Hazen’s  Popular  Tscbnologyj 

or.  Professions  and  Trades.  Illustrated  by  81  Engravingik 
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Henry’s  History  of  Philosophy. 

Epitome  of  the  History  of  Philosophy.  Being  the  Work  adopt- 
ed by  the  University  of  France  for  Instruction  in  the  Colleges 
and  High  Schools.  Translated  from  the  French,  with  Addi- 
ctions, and  a Continuation  of  the  History.  2 vols.  18mo,  Mus- 
lin, 90  cents. 

Herschel’s  Natural  Philosophy. 

A Preliminary  Discourse  on  the  Study  of  Katural  Philosophy. 
12mo,  Muslin,  60  cents. 

Kane’s  Elements  of  Chemistry; 

including  the  most  recent  Discoveries,  and  Applications  of  the 
Science  to  Medicine  and  Pharmacy,  and  to  the  Arts.  Edited 
by  John  W.  Draper,  M.D.  With  about  250  Woodcuts.  8vo, 
Muslin,  |1  50;  Sheep  extra,  $1  V5. 

Eeightley’s  History  of  England, 

from  the  earliest  Period  to  1839.  With  Kotes,  <kc.,  by  an 
American.  6 vols.  18mo,  Muslin,  $2  25. 

Lee’s  Elements  of  G-eology, 

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Lewis’s  Platonic  Theology. 

Plato  contra  Atheos.  Plato  against  the  Atheists ; or,  the  Tenth 
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Uotes,  and  followed  by  extended  Dissertations  on  some  of  the 
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Liddell  and  Scott’s  Greek-English  Lexicon, 

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Authors,  by  Henry  Drisler,  M.A.  Royal  8vo,  Sheep  extra, 
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Loomis’s  Mathematical  Series. 

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Elements  of  Geometry  and  Conic  Sections.  8vo,  Sheep  extra,  75 
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Introduction  to  Practical  Astronomy.  8vo,  Sheep  extra.  (In  press.) 

The  Recent  Progress  of  Astronomy,  especially  in  the  United  States. 
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Elements  of  Plane  and  Spherical  Trigonometry.  8vo,  Sheep  extra, 

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Elements  of  Plane  and  Spherical  Trig- 
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The  Rel'Ent  Progress  of  Astronomy. 
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DRAPER’S  CHEMISTRY.  300  Illustra- 
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DRAPER’S  NATURAL  PHILOSOPHY. 
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DRAPER’S  CHEMICAL  ORG-ANIZA- 
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GRAY  S NATURAL  PHILOSOPHY.  360 
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GRISOOM’S  ANIMAL  MECHANISM. 
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HAZEN’S  POPULAR  TECHNOLOGY. 
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FOWLER’S  ENGLISH  LANGUAGE,  in 
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MILL’S  LOGIC.  8vo,  Muslin,  $I  50. 

PARKER’S  AIDS  TO  ENGLISH  COMPO- 
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WHATELY’S  ELEMENTS  OF  LOGIC. 
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LOSSING’S  PICTORIAL  FIELD-BOOK 
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for  Independence.  2 vols.  Royal  8vo,  Mus- 
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GOODRICH'S  SELECT  BRITISH  ELO- 
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entire  of  the  most  Eminent  Orators  of  Great 
Britain  for  the  last  two  Centuries : with 
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PRESCOTT’S  WORKS. 

History  of  the  Conquest  of  Peru.  2 vols. 
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Calf,  $5  00.  — History  of  the  Conquest  of 
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POTTER’S  HAND-BOOK,  for  Readers  and 
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SALKELD’S  FIRST  BOOK  IN  SPANISH. 
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STORY  ON  THE  CONSTITUTION  OF 
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Reign  of  Ferdinand  and  Isabella.  3 vols. 
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HILDRETH’S  HISTORY  OF  THE 
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SPARKS'S  AMERICAN  BIOGRAPHY. 
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